Looking at the old fashioned TV, I'm wondering if I've discovered the Hand Dance Pro a little late. Anyway, these are super expensive but use arcade standard parts, so should stand up to a good beating. Alternatives are the Mini DDR mat or building one yourself by hacking large on/off buttons to the contacts of a cheapo fold-up dance mat.
Read more at: Exergame Fitness, Cobalt Flux, Fitness Gaming, Motion Kids, Palos Sports and S&S Discount PE Superstore.
Update: Still available at this time for $499.99 USD (Product code CFHP1) according to Zak Wellard of Cobalt Flux.