Hey guys, I was randomly looking at lifehacker today and found an interesting post that might be of interest to you guys. It's called zaptxt and allows you to be notified by cell phone sms when something matching your criteria comes up on craigslist, blogs, etc. I havent used it yet, but this should help people looking for old used bikes.

ZapTXT: RSS Filtering and Notification.

ZapTXT allows you to define search criteria for your RSS feeds and OPML and then notifies you via email, SMS or IM when a new entry contains your search keywords.

ZapTXT connects you to leading web services:

Too many blogs? Reduce your blog overload by having ZapTXT do the monitoring and filtering for you. You can read what you want and ignore the rest.
Want to be the first to reply? Stay on top of Craig's community by monitoring specific categories -- ‘for sale’ items, events, housing, jobs -- and getting alerts via email, IM or SMS when a post meets your criteria.
Tired of having to check multiple sites to find that perfect [job, couch, lava lamp, etc.]? Monitor any RSS enabled classifieds site for specific items. ZapTXT does the work of monitoring and screening. You just wait for the email, SMS or IM!
I guess the only downside is you have to know what you're looking for, but i'm sure this could help.