locked by Matthew Read♦ Dec 11 '12 at 15:40
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closed as not constructive by Matthew Read♦ Oct 3 '12 at 22:51
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Here's a good one I found on Lifehacker a while back.
I changed a few things when I did it, like allow the text to come from any phone and send the reply to that phone, and making the SOS text a passphrase so that nobody accidentally sent it to me.
I also made one that turned my ringer up and played a song for when I lose my phone around the house. I can just text my phone 123findme and it will play a song even if I left it on vibrate mode.
I just posted a couple of profiles in an answer to another question that together allow for the handset's location to be periodically checked then sent via SMS or HTTP. The profiles enable GPS if needed then power it down again when done.