I would prefer something less bulky (I don’t wear a watch) but thank you for the link: that is indeed dirt cheap and probably worth a go.

I guess it depends. My partner still gets woken up by my (smart)watch at the lowest vibration setting.

If your partner gets woken by a watch vibration actuator, I doubt it's possible for you to sneak out of bed without waking them, as your body weighs about 10,000 times as much as that actuator.