From my own research (still too broke to make my own purchases), I've read that vibrating panties are fairly wimpy and make noise and vibrations, but not enough that's going to do anything crazy. I'd get a vibrating bullet and only put it on her clit and in loud places, or keep it in her cunt to keep the noise down. That, or there are "butterflies" that are often shaped like butterflies and have thigh straps that look kinda like wings to keep it strapped on and centered on her clit. Just look at all the normal bdsm sex toy places, extreme restraints, or something like that.

My personal favorite though is the Oyster line of remote control vibes

If I had the cash, I'd go for that, it was featured on several british tv specials too lol.