Nudge is described as 'Make the internet less addictive with nudges that help you avoid getting sucked in'. There are five alternatives to Nudge for a variety of platforms, including Windows, Android, Mac, Linux and Online / Web-based. The best alternative is ActivityWatch, which is both free and Open Source. Other great apps like Nudge are RescueTime (Freemium), Timeular (Paid), HabitLab (Free, Open Source) and Time Arrest (Free).
ActivityWatch is an app that automatically tracks how you spend time on your devices. It is open source, privacy-first, cross-platform, and a great alternative to services like RescueTime, ManicTime, and WakaTime.
xTime is a windows application that track your daily activity in your computer and helps you remeber what you did and helps you on your timesheet entries. Capture Office Word, Outlook, PowerPoint, Excel, Chrome, etc.