Are there any small tracking devices I could buy, and put on an iphone?

My Iphone was stolen today, and they immediately turned it off so there's no way of tracking it with "Where's my Iphone". I'm wondering if there are any small almost invisible tracking devices that I can put underneath my case that will help me find my phones if they are stolen in the future.

The thing is, "Find My iPhone" is an incredibly powerful software. Although they may have turned the phone off, you can always check every few hours if it's turned back on. Eventually it will have to be powered up again even if they sell it to someone.

In regard to a "small almost invisible tracking device" the answer is no. Although there are incredibly compact GPS tracking devices like this one http://compare.ebay.com/...s&var=sbar they are only slightly smaller than the size of a hand. It would most likely be as big or slightly smaller than an iPhone.

Find My iPhone is your best bet and has actually worked for me once or twice when stolen or lost.