I have been searching for a really small receiver and have been doing research. Thus far, this appears to be the best that I have come across (especially for it's size):
Freedom Mini Keychain GPS
http://freedominput.com/site/index.p...d=96&Itemid=81
Here is an excellent review over at TC:
http://www.treocentral.com/content/Stories/1363-1.htm
Much Luv,
iZm