Hotone have added Tap tempo to Xtomp with their latest update. This means you can tap in the speed of all your time based effects such as delays.
This is available as a free update to the Hotone app for iOS and Android - but remember to update your firmware as well as the Xtomp app; this is vital to maintaining full functionality of your Xtomp. Go to the app's "Settings" page and click the "check update" button.
Click here for more information about Xtomp