From having briefly looked at the code, db.GetObjects only accepts a whitelist of IDs to look up.
I suppose you could submit a Pull Request, but if the same feature is not available in Redis then you are creating a feature that only exists in some of the supported storage systems, which increases complexity of the NodeBB project.

It looks like NodeJS + MongoDB does support query by RegExp.
My guess is that you would want to detect the data type of the first parameter passed into db.GetObjects similar to the following:

re = new RegExp('.');
'object' === typeof re && re instanceof RegExp;

nodebb-plugin-stockparser parses UGC for StockTwit-style stock tickers and replaces them with a link to the stock detail page.

Can anyone point me to a plugin that already has an admin panel page which has an editable field where I can define a URL pattern? TIA

The only thing that came to mind was the possibility of pjax (partial page reloads) where the iframe or the original scripts were removed from the page when part of the page's content was reloaded.
I don't know enough about NodeBB yet and haven't had time to investigate. That and I detest turning off AdBlock.

Update:
My guess is this either has to be solved in the nodebb/package.json or in the npm configuration for the two theme modules.

Here is what you get when you try to npm install with the included nodebb/package.json:

npm ERR! notarget No compatible version found: nodebb-theme-vanilla@'>=2.0.19 <3.0.0'
npm ERR! notarget ["0.0.1", ... ,"2.0.10","2.0.11","2.0.12","2.0.13","2.0.14","2.0.15","2.0.16","3.0.0","3.0.1"]

and if I fix the nodebb-theme-persona version, I get this on the nextnpm install` right now:

npm ERR! notarget No compatible version found: nodebb-theme-vanilla@'>=2.0.19 <3.0.0'
npm ERR! notarget Valid install targets:
npm ERR! notarget ["0.0.1",...,"2.0.1","2.0.2","2.0.3","2.0.4","2.0.5","2.0.6","2.0.7","2.0.8","2.0.9","2.0.10","2.0.11","2.0.12","2.0.13","2.0.14","2.0.15","2.0.16","3.0.0","3.0.1"]

I was able to fix this by altering my nodebb/package.json from:

    "nodebb-theme-persona": "^1.0.24",
    "nodebb-theme-vanilla": "^2.0.19",

to

    "nodebb-theme-persona": "^1.0.21",
    "nodebb-theme-vanilla": "^2.0.16",

What is very strange:
npm info nodebb-theme-persona:

  versions: 
...
     '1.0.14',
     '1.0.15',
     '1.0.16',
     '1.0.17',
     '1.0.18',
     '1.0.19',
     '1.0.20',
     '1.0.21',
     '2.0.0',
     '2.0.1',
     '2.0.2',
     '2.0.3' ],

  time: 
...
     '1.0.19': '2015-07-27T19:34:23.624Z',
     '1.0.20': '2015-07-28T13:34:58.458Z',
     '1.0.21': '2015-07-28T14:12:42.725Z',
     '1.0.22': '2015-07-29T16:42:57.039Z',
     '1.0.23': '2015-07-29T16:59:15.254Z',
     '1.0.24': '2015-07-29T19:21:23.722Z',
     '1.0.25': '2015-07-29T20:49:05.755Z',
     '1.0.26': '2015-07-30T19:25:36.378Z',
     '2.0.0': '2015-08-04T14:41:11.480Z',
     '2.0.1': '2015-08-04T14:50:34.904Z',
     '2.0.2': '2015-08-06T20:40:24.259Z',
     '2.0.3': '2015-08-07T04:36:23.502Z' },

Notice the all show up under the time field of , but not under the versions field. I'm fairly sure this is why npm install doesn't find a suitable version of the npm modules / nodebb plugins to install.

Output from npm info nodebb-theme-vanilla:

  versions: 
...
     '2.0.10',
     '2.0.11',
     '2.0.12',
     '2.0.13',
     '2.0.14',
     '2.0.15',
     '2.0.16',
     '3.0.0',
     '3.0.1' ],

  time: 
...
     '2.0.16': '2015-07-28T13:34:41.548Z',
     '2.0.17': '2015-07-29T15:31:44.952Z',
     '2.0.18': '2015-07-29T16:42:17.123Z',
     '2.0.19': '2015-07-29T16:58:55.254Z',
     '2.0.20': '2015-07-30T19:26:37.250Z',
     '3.0.0': '2015-08-04T14:32:22.192Z',
     '3.0.1': '2015-08-04T14:49:45.409Z' },

Notice the npm install errors come from versions missing, but there are keys in the time dict.

NodeBB's package.json has the entries:

    "nodebb-theme-persona": "^1.0.24",
    "nodebb-theme-vanilla": "^2.0.19",

Both of these themes just updated their newest NPM version numbers to new major versions in the past 6 days.

It's possible to manually npm uninstall nodebb-theme-persona then npm install nodebb-theme-persona@1.0.21 (notice the @1.0.21, explicitly requiring a version of the package to be installed)., but this is overridden and lost at the next npm install.

I'm currently looking at NPM docs for package.json and NPM docs for semver -- caret ranges. Neither seems to address the problem where NPM automatically updates modules above the necessary required versions defined in the package.json in the nodebb directory.

Can a NodeBB developer or someone well versed in NPM packages+versioning weigh in on this?

I don't know of any plugin that is already built to do what you want. Like most of the rest of us, you will likely have to write some Node JavaScript to create the plugin to suit your needs. I don't have the time to write custom code for free, although if it is worth money to you, the NodeBB development team may be interested in consulting for you.
Now that I re-read what you originally asked, I'm curious if you actually need "Sockets" (as in SocketIO, which is server-initiated TCP/IP connection to a browser) or if APIs on both the hosted NodeBB server and the localhost server would do this better.
Either way, if you choose to go the NodeBB plugin route, you will need to know which Hooks are available. A "hook" is an event that your plugin subscribes to. When that event happens in the core NodeBB server, it will call the function in your plugin which subscribes to the event.

I'm not sure if I understand your question exactly, but you can write a plugin to listen to a new route (URL endpoint) or interprocess communication and load and call NodeBB libraries.
You may consider using this plugin Git repo as a bootstrap to get you started quickly. Remember that the plugin.json, package.json, and library.js are the first files to work with. The plugin repo name / directory name will need to match the glob nodebb-plugin-* and it needs to be directly under the node_modules/ directory which is at the root of your NodeBB directory.

@ahmed_commando It sounds like you will probably want to look into NodeBB plugin development. A NodeBB plugin can either hook into the SocketIO the NodeBB server is handling for reading or it can generate its own content for sending.

nodebb-plugin-stockparser parses UGC for StockTwit-style stock tickers and replaces them with a link to the stock detail page.

Can anyone point me to a plugin that already has an admin panel page which has an editable field where I can define a URL pattern? TIA

@d3athwarrior Did something change recently or has this been the case since you installed NodeBB?

From having briefly looked at the code, db.GetObjects only accepts a whitelist of IDs to look up.
I suppose you could submit a Pull Request, but if the same feature is not available in Redis then you are creating a feature that only exists in some of the supported storage systems, which increases complexity of the NodeBB project.

It looks like NodeJS + MongoDB does support query by RegExp.
My guess is that you would want to detect the data type of the first parameter passed into db.GetObjects similar to the following:

re = new RegExp('.');
'object' === typeof re && re instanceof RegExp;