Would be cool if that would be possible, it's a feature I really miss a lot in all other such apps.
Yammi has/had used XML as the storage backend, probably loading the whole "database" into memory, which obviously might sound a bit heavy on memory but is very fast (and I never saw memory problems with it).
The fuzzy search code it used is at http://yammi.cvs.sourceforge.net/yammi/kyammi/src/fuzzsrc... and is under the GPLv2 (but I guess Oliver might be open to relicensing if you need a different license).
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