The BT (Bluetooth) Small Switch from RJ Cooper is an inexpensive but very functional switch to control iPad (iPad 3 and above) and Android tablets.
This 3″ fairly-light touch switch can easily be put into 6 modes:
(for Select), (for step-scan), (Music, YouTube, Pandora, etc.), (iPad Camera app), (Select for VoiceOver/Switch Control), (previous item for VoiceOver/Switch Control), (next item for VoiceOver/Switch Control, Home.
Pairing is simple and persistent.