We've talked about AIDE, the mobile developer toolkit that allows you to write Android apps (almost) entirely on your phone or tablet. In those past discussions, we've mentioned that you can probably get by with just the free version. The premium key offers a few nice extra features, though, like APK publishing, Git push/commit, and saving large project files.
Most of the features of the premium version are handy if you want to code entirely on your mobile devices which, admittedly, most of you probably won't want to do. Ideally, this app works as a companion to your typical IDE (like Eclipse), but while this sale is going on, it's a small price to pay for a little extra convenience.
If you want to get in on this deal, you'll need to install the free version via the first widget below. The Premium Key is a separate purchase and only unlocks the extra features. It's not the app itself. Grab it from the second widget.