Eno ET-3000 clip on tuners
I have three of these guys:
They’re great. Very, very useful and no faffing around plugging guitars in and out of tuners. SGD $28 man… I bought mine at Maestro guitars in Excelsior shopping centre basement but I’ve seen them in a few places. They detect the vibration of the headstock and use that to tune to. The screen turns green or red depending how far off the target note you are. You can also switch modes so that it tunes via a little onboard microphone.