I just discovered yesterday that an intervalometer exist on pyKake, but works via infrared. Maybe you can take a leaf out of their book to help with the USB host version of your intervalometer...

Would love to do the tethering. But it's a bit complicated to get it setup at this stage like you have described. If/when somebody makes this installable via app manager, I'll definately jump on board. There's a nice youtube vid of a time lapse showing ice cubes melting. Was that you?

Cheers,
Fred