Discrete bondage

[GaryWilcox]

There are vibrators with remote controls, of course...

There's an excellent chastity belt that delivers punishment shocks for the truly daring...

You could invest in a wheelchair, and be bound by hands and feet if you wish. Would recommend trying that on vacation in a far off city, as someone you know seeing you might have a bad reaction to seeing you in a wheelchair.

[le forgeron]

You could invest in a wheelchair, and be bound by hands and feet if you wish. Would recommend trying that on vacation in a far off city, as someone you know seeing you might have a bad reaction to seeing you in a wheelchair.

Without the wheelchair, you could simply use medical minerva and plaster.
The minerva is probably the easiest to deal with (Not THAT sexy leather minerva, just the plain medical one from the paramedic): you could always pretend to have a stiff neck, that's a condition which might disappear the day after if you ever cross again someone you know.
Plaster (or resin) on arms or legs is not so discrete, and explanations for the curious is more difficult to come with, expecially for a short period (but might be interesting for something like a two-week uninterrupted restrains: beware of muscular lost, you will need some progressive reinforcement).
Of course there is always that pratical joke of student physicist: plastering someone's arm while s/he sleep, upon wakeup, s/he has to wait something like 6 or 7 hours for the plaster to dry before being able to remove it properly

That's was just an idea triggered by the wheelchair.