Not having a cell phone, I can be a bit behind when it comes mobile apps - but this is still cool even to tech-no's like me.
My former co-worker Chris pointed out the iPhone app RedLaser, that turns the iPhone's camera into a barcode scanner. The app was designed to do instant price checks while you're in a store, to see if you could buy something cheaper online.
So a patron with an iPhone (or an Android) could be shopping in a bookstore, see a book they'd like to read, and instantly scan it to see if it's available at their local library. Great stuff.
But wait, there's more...
Another colleague, Scott Kehoe of NMRLS, posted about making customized versions that can search the MVLC (my library consortium), MassCat and the NOBLE consortium catalog. His post shows how he did it, links to Delicious for the customized databases, and explains how you can customize it yourself.
I think this is a great thing to promote to patrons, but they need to be careful about walking around bookstores scanning barcodes. I've heard many stores will throw people out if they appear to be doing "research" (recording a store's prices or looking for country of origin). Also, about this app, one bookstore owner was quoted as saying:
If I see any lecherous internet bottomfeeders using my store as a display case for a discount website, I will politely ask them to leave.
As the world of mobile devices becomes more compatible with the world of ebooks, the next step will be to create customs searches of places like Overdrive and Project Gutenberg, so that patrons can not just locate but also download the desired book immediately. I tend to think instant gratification is not a good thing, but in this day and age, it is certainly easy to support.
For a few more library-related apps, check out Aaron's post on Walking Paper.