You need to upgrade to PRO (IAP purchase inside app). With Pro you can unlock supported apps: iTunes, Spotify, Deezer, VOX, VLC, Beamer.
You can pair more devices and switch between them directly from Today Extension in iOS Notification Center.
To enable this feature you need upgrade to PRO from Settings in iOS app.
If you don't want to upgrade, you can still delete your first added device by swipe left on table cell in Settings.
Restart your iPhone/iPad. In worst case you can try reinstalling TodayRemote iOS app.
For feature request or support: firstname.lastname@example.org