podcasting, registered users and audio-coupons?

Adam Curry has been talking a lot about a new service that will soon be made pubic called "my podshow". The idea is that through a subscription mechanism, podshow.com will be able to "report" somehow how many listeners are subscribed to each podcast. Which by itself sounds interesting. From what I've understood so far, podshow will be able to "cash out" this information by putting ads in podcasts.

This is where my idea of "personalized audio coupons" comes in. If podshow had a way to "attach" a personalized audio coupon with a code to each subscriber, marketeers would be able to mesure the effect of a campaign through a podcast! It is not easy, but it should not be so difficult to implement, what you basicly need is some speech syntesis software to create the small audio chunk containing the persinalized promo code and then a way to attach this chnk to the original audio file.

Well? What do you think?