Phone as a GPS tracker
Have you tried Tasker? I actually have a task set up exactly for this in case I lose/forget my phone, where if I send an specific message (so that I don't do it by accident), the app automatically gets my location and sends the co-ordinates to the sender of the message. 

You said you also want it to automatically turn on GPS, so you might need to root your phone to do that depending on how old your phone is because after Android 2.3 apps can't change GPS without root.