I use a TK102 Tracker. Like similar devices it operates on a GSM network. T-Mobile is the only one who offers that service now and it works great. You call it and it hangs up and sends you a text with a google maps link. It's spot one.
One thing that is cool is it has a built in mic. You can turn it on and hear what's around the tracker. So if you go where it says you drone is located and you don't see it right off you can turn the mic on and listen on your cell phone. Just give out a holler to hear when you get closer.
I have been using mine for 3 years on a P2 and getting ready to add a second one on my P3.
By the way the device is only $20 and you get a T-mobile starter SIM kit for $10. You can put as little as $3 a month in the T-Mobile account. It's a pay as you go no contract. I opt to add $100 to my account and it will not expire for 13 months. Each text costs you 10 cents.