Changelog Droid, an app that not only shows changelogs of applications you have installed all in one convenient place but also monitors apps that you haven't installed and keeps history of changes over time, is on sale for 24 hours. And by sale I mean it'll cost you about free fifty. I've played around with the app for the last half an hour and found it to be very polished, pleasant to use, and, more importantly, actually handy. It even has a DashClock extension.
Since the Play Store doesn't allow apps to switch from free to paid, the developer is using the next best method - a coupon code. Usually, the downside of this is that if you uninstall and reinstall later or install to another device once the coupon expires, you will likely lose the paid features. Speaking of which, the $1.87 premium license removes ads and adds support for themes.
If I were you, I'd use something like Titanium Backup or Helium (the latter doesn't even need root) to back up and restore this app in the future. In this case, the developer went the extra mile and made sure that any entered coupon codes with be forever associated with your Google account. Thank you, Cypressious.
To get Changelog Droid Premium for free, load up the free Changelog Droid app and enter code appoftheday by going to Menu -> Preferences.