1) Triangulation, a number of masts/base stations, simply calculate the rough position based on ping time and angles can be calculated using just pythagoras. Realy limited to the phone companies who own the masts / anyone with knowledge of the systems.
2) GPS - well, only if the phone has it active 24/7/365 and you happen to be able to look up a device connected to a GPS satellite... Let me guess probably not?
I am surpised no one has written an app for losing their phone with GPS to tell them where it is, not that there is any easy way to implement that...
There are plenty of mobile tracking apps for android, and am sure there are plenty for the iphone. It isn't too hard to write something like that yourself either; you could choose your own delivery method for your logs.