R – monitor wireless network usage

You might find this project interesting. It is just a .NET wrapper on the native API. You should be able to call this from PowerShell without too much trouble:

http://managedwifi.codeplex.com/

I would prefer to write an Application which is going to Connect at you're Router. You can do it in 2 ways
1. Web Interface
2. Telnet Client

Using Web Interface WebRequest and Regex are you're friends where you can get from Router Connected Client's. Or using Telnet Client where Sockets is you're friend in this case . In both way's you can get any message you want and store them in a String where you can filter later .