I just think back to my time in the Boy Scouts. We used to print out a sheet for every Scout every other meeting, showing them what requirements they had completed and which ones they still needed to advance to the next rank. We finally re-did our old, single page website into a more full-featured application. Scouts could now see the troop roster online, check requirements, access knowledge banks with packing lists, and more.
But no one brings computers to the meetings, and the site is just too complex to navigate on your smartphone. Propeller would be the perfect tool for them, because many of the Scouts have a smartphone and bring it to each meeting, and would be able to access the information just when they needed it the most.
I'm sure you all know of organizations like the one I just described. But do you know any mobile developers who are interested in helping them? The money just isn't there. The glamour isn't there. But these apps still need to be built. THAT'S why I think Propeller will sine.
This is explicitly forbidden in the iPhone app store. Actually distributing these apps will be a problem; code signing and adhoc and/or appstore distribution is a complex and distinctly non-user-friendly activity.