Re: GSM Desktop Phone Set
You need a cell phone with "900" frequency and it needs to be UNLOCKED.
There are lots and lots of phones that have 900 frequency, so fidning one shouldn't be a problem in USA.
If you buy a phone from a retailer such as T-mobile, its is LOCKED. Which means it is programmed to work only with T-Mobile. You can get it unlocked in Pakistan for quite cheap (couple of $ if they rip you off) or it should be about $10-$20USD in states if someone private does it. (Cingular or T-Mobile ... one of them actually give you the code to unlock for free, if you ask).
Let me know if need help with phone selection etc. If you get a nokia phone, I might be able to unlock it for free for you.