it's a cool idea ~ but the problem is that eeeeeveryone's bodies react differently in the build up to orgasm.. plus if you're using a vibrator it's easiest to manage the amount of teasing you get with your own hands ... backing off and starting up again when it suits...
i always thought the people at ann summers were on to something with the rampant rabbit ~ the newer ones have a setting that gives "irregular" pulses of vibration... of course its a repeating pattern of short, short, short, long (or somethign like that) so after a few seconds you get to know when the long vibration is coming... a totally irregular and unpredictable setting would be awesome!