Regardless of whether you use Amazon's app store for Android, there's no denying that a free app every day is a good deal. Of course, sometimes the deals are better than usual. Today's free app of the day is Servers Ultimate Pro, which is normally $8.99.
For those not acquainted with the app, it allows users to run servers from their mobile device, with over 70 protocols supported (see the full list in the app's description), and a heaping handful of network tools. The app does require root for a few protocols (like VNC and VPN), but otherwise Servers Ultimate Pro doesn't have very many limitations.
Servers Ultimate Pro is definitely a niche app - not everyone is interested in running servers from their phone, but if you are or think you may be in the future, you'd be well-advised to go ahead and grab the app while it's free.