Cannot agree more with wishcan. I sketched up a few different ideas for something like this, but never pushed on because I thought integrating with hotels, airlines, etc. Would painful. Also figured I'd need to automatically parse email confirmations, which would be a PITA.
What is it written in and how much work is left to do?
I often wondered if automating the pain point you mention above (integrating with hotels, airlines etc.) and providing a singular, specialized API for that would be an amazing business opportunity. Seems like one of the existing travel companies could do it, or a travel agency.
Strikes me that you could turn this around somewhat...
When people are publishing what they want, that looks to be a good starting point for travel/lodging companies to come in and make offers to these folks.
"You're looking to stay in Bucharest on Sept 18 and 19? Our hotel can offer you XZY for $ABC on those nights."
Sort of like lendingtree-model for travel. Not quite sure why that's not taken off yet, other than, perhaps, larger company IT systems?
This could possibly work well for smaller regions - contact a local chamber of commerce and have them have all the local businesses make offers to people looking to stay in areas on specific days.
Basically... define a format and let them integrate with you if they want access to the market you've defined, not the other way around.
What is it written in and how much work is left to do?