I've been a user since it was a Kickstarter project. It works quite well, actually. The device comes with a globally activated SIM card inside that sends an email/sms to you every time in you in a new location. There's also an Android/iPhone app that has a a bluetooth locator that you can pair with the device so you can track the proximity of your luggage inside the airport. The location is also shown on the app but it's just a webview of the website.

The FAQ says: "...device emits a signal that is used to determine its location, but does not use GPS."

Anybody knowledgeable can throw light on what kind of signal it could be?

Ah never mind. It says later on "The device will not operate in countries where GSM does not function."

wow $50 is a solid price point and puts it in impulse purchase zone for a lot of people. I figured it'd be $100 or more. Not for me as I don't travel enough with checked bags, but still, props to the founders.