What is it you want to figure out? What she is saying to him? If/where she's meeting up with him? What?
WHAT you need to know will determine what you USE to get it.
Not sure what you mean by "spy phone." But for less than $50, you can get a GPS-enabled, pay-as-you-go phone (BoostMobile) with a pretty robust GPS tracking software (MapQuest FindMe) on it.
