Even in a pure software company, someone should be out there validating the idea, building a client list, etc... In this case, it could be those and things like prepping for a kickstarter campaign, storyboarding, and of course the hardware development. There is always more to be done.
In regards to #3, in the example given, if OP wants to be cofounder then to some degree this makes sense but if not, it gets a bit more tricky. My advice to OP here is to figure out how much commitment you actually want to put in and ask for equity split (vested among all members) accordingly.