Hi there,
I'm not sure if you're asking whether this is possible, and if so how to do it, or just asking if it's a good idea. Whether it's a good idea or not depends on what you're trying to do with it (which you haven't said). It is certainly possible to simply poll your USB Bluetooth chip for what devices are currently in range (should be one of the easiest things to do, especially if you have found a library for doing it) and then simply check in that list for your device. It should be simple and easy.
However, it is very fundamentally flawed if you are wanting to use this as a reliable way for detecting your presence. It is probably easiest to get a list of device names that are within range. However, this would allow any device with the same name as yours to look exactly like yours, thus spoofing your presence. You may be able to get a list of device Ids instead, but that is susceptible to the same problem (Id spoofing). So this really isn't a good idea if you are trying to use it for security purposes etc.
If your phone is a smart phone you could write an app for it that will communicate with your computer when it is in range and use public key/private key encryption and your own certificates system for your phone/computer. Unfortunately this is then neither simple nor easy.
Hope this helps,
Ed
Oh by the way, I looked up the library you are using. Here's the documentation page that you want:
http://32feet.codeplex.com/wikipage?title=Discovery&referringTitle=Documentation[
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Just convert the samples from VVB.Net to C# - not very hard...