Japanese toymaker Bandai's Mugen Puchi-Puchi is a handheld electronic gizmo that makes the sound of popping bubblewrap when you press on the plastic bubbles. From Mainichi Daily News:
…Once in every 100 squeezes of an air bubble, instead of emitting a "popping" sound, the noise will be replaced by the sound of a fart or a woman moaning in ecstasy.To avoid any embarrassing situations, Sunday Mainichi notes that Mugen Puchi Puchi's are made to automatically turn off the sound on the train, so people can squeeze their air bubbles in peace knowing that they're not going to produce any unseemly noises.
Link to Mainichi Daily News, Link to pre-order Puchi Puchi from StrapYa.com (Thanks, Paul Saffo!)