Works really well, nice and quick. Call me stupid, but I'm not actually sure how to launch it (clicking on "Launch App" from within the webstore works but that's surely not the only way).
oh, good idea. I wonder if navigator.registerProtocolHandler works in apps?
I tried adding it manually in settings->Content Settings...->Handlers, but it only allows you to select handlers on sites that have already requested permission, not add new ones (as far as I can tell).