It’s not a fully functional toggle to allow you to go back and forth from 4G to 3G without leaving your home screen, it acts as a shortcut and is a little bit faster then going into Settings > Wireless & Networks > Mobile Networks and change to CDMA only for 3G or CMDA/LTE for 4G.
This toggle has been tested to work on the Droid Razr Maxx and the Droid Bionic ( I haven’t tried it on any other devices), and of course it works on the Droid Razr since it was made for the original Droid Razr. It’s free from the market, and currently the only option for those of us with Motorola devices, and at just 29kb in size it’s worth it to save a few steps when turning on/off 4G on your Motorola Droid device.
If you’re interested, hit the source link and download it and let us know how much you like or dislike it. Don’t forget to provide feedback to the developer so they can make it better, that is how bugs get fixed.