I've never tried one, so I don't know if they interfere with strumming or not. However, MiSi and LR Baggs make sound hole pickups as well, so they must not be too problematic?
The HMS video sounded pretty cool. Not having to deal with cables & amps, but being able to shape the sound a little would be cool in some situations. Just this past weekend I went to a uke jam, but didn't bring my uke with a pickup. When I got there the leader asked if I wanted to play a solo & did I bring a uke I could plug into his amp. Yes to playing a solo, but no to bringing a uke I could plug in. One instance where that Leolani might come in handy.