Yes, that's how Lookout or Seekdroid (or any of them) work. If your phone is on (and Background data is on), it can send a text to turn on GPS on the missing phone, and then let's you know where it is on a map. Can be accessed from another phone or on a PC from their website. You can also tell it to set an alarm off, or wipe all your data. I don't use anything since I always have my background data off, so hope I don't lose it.