TextLoc

You or your friends can now easily track your phone's location via text message.
Simply add your friend's phone number as "trusted numbers".
Upon receiving a text message with content "where are you", from any of the trusted numbers
the app will automatically reply with current location via the text message.

No Data is required when tracking the current location - this is done solely through GPS satellite, network tower, and Wi-Fi.
You do not need to create any account, and your friends do not need to install any app.

This is perfect for phones without data plan.