This is OpenTable's fight to lose but we could see a world in which different apps win different cities. Still waiting to see if any can take this national.
This is an idea that startups often try and quickly abandon (see Toast in Boston). The clear winner in Manhattan is Cover - I think this is exactly what you're looking for.
TabbedOut and MyCheck have really struggled to get any real traction here in New York. I saw recently that Cover does more volume in Manhattan than all the competition combined. Not sure if there are any good options in SF.
Interchange zero was such a weird move. They were losing money on every transaction and they decided to get to scale by losing even more money on even more transactions!
When SCVNGR pivoted from daily deals to this it seems they forgot to pick up a business model on the way.