What about using an infrared "trip wire" near the figure? That could probably be hooked up to software on a computer (Pentium 90) to trigger playback of an MP3. Cost = trip wire only, since everyone's got P90's lying around for spare. And a huge hulking figure of Borat could easily hide all the necessary guts.
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FireFox31
110gig MKIIa (30+80), Eutronix lights, 32 meg stacked RAM, Filener orange gel lens, Greenlights Lit Buttons green set