Good, they need to get with a GSM carrier so they can get iPhone users.

Loopt wont work on the iPhone yet (natively), because it requires GPS hardware (which the iPhone does not yet have). Hopefully someday though, its a cool app.

Doesn't it work on some phones that have APIs for a triangulated, interpolated GPS?

I havent heard about that, but if thats the case and you find out more please share. It might be proprietary code rather than an official optional library.