Strider version 0.0.2 adds a menu for changing the steps per minute as well as the vibration strength. Many Garmin watches have a menu button, but some don't. The supported devices should all have a way to open a menu though. For example, for the Forerunner 235 a menu can be opened by holding down the up arrow for some time.
After using the app for some time, I've found that whenever the watch has a lag spike the timer can pause for a little bit. It doesn't happen too often, but I'll look into fixing it. On some devices the UI doesn't look very good yet, but the goal is to eventually make the app look clean on all devices. Working on the project solo currently, this may take some time. Any help with this project would be greatly appreciated!
Download the app at: https://apps.garmin.com/en-US/apps/f155897d-002a-4465-8271-6271b0d8909c