This concept is brilliant. If I lived in one of the current markets (San Fran, NY, LA, Philly, Boston, Chicago, Miami) I would absolutely download this app and sign up for Gigwalk.
The concept is simple - use the app and the iPhone to outsource small, real-time, real-world tasks for money. Seems to be the natural next evolution of crowd-sourcing. You've got an army of iPhone users all over the world. They're constantly on their phones, constantly moving about and interacting in the world. Offer to pay them to verify information or perform basic tasks. Perfect!
This is far fetched, but I can imagine a company using a bunch of iPhone Gigwalk users as their in-the-field eyes to monitor how their products are placed in stores, etc. Where once they had been flying employees all over the country to check on product placements, etc., now they're simply offering small cash to people already in those locations, already shopping at those establishments. I love it.
Bravo to an innovative idea.