Use the Tweet Scan API to get search results from Tweet Scan. Tweet Scan is a real-time search engine for Twitter, identi.ca, and eight other Laconica-based sites (the eight other sites being The TWIT Army Canteen, bleeper.de, fun.ohhh.no, Suffice to Say, Lareta.net, Linux Outlaws, MicroCiaran, and Pawwer).
Those worried about the longevity of their tweets have another reason to relax. The Social Archive, which also stores status messages for many StatusNet-powered sites, is entering the Twitter search game. It joins Topsy, Tweet Scan and Twitter's own search engine, which received a recent upgrade.