I disagree about needing a mount. It'll work out costly and, imho, will need a LOT of work to get it looking good.
Unless you're using a bullet-cam with a fixed focal length, you'll need a proper operator to accurately line up the shots and pull focus etc. And the quality of footage from a bullet-cam will never tally with the footage from your main camera.
If any of you are familiar with the UK comedy 'Peep Show', then you'll know that they shoot it entirely
first person - and very little of it is achieved with rigs and minicams.
Check out this behind the scenes video
- the way they the majority of the show is by having the camera take the place
of the actor, who just ducks his hands into and out of shot at the necessary moments. It takes time and a lot of rehearsal, but you can get it looking very smooth. For shots where you need the actor to use both hands, just place the camera on their shoulder and look 'down' at their hands. It's not practical for all shots (i.e. anything where you need to move the actor any significant distance) - but for shots where they're rifling papers or whatever, it works just fine. You just need to think through what shots you can achieve with just the camera, and where you'll actively need both hands from the actor, and then from that, work out where your edit points are.
Oh, and bear in mind that whip pans are great ways of doing 'invisible edits' between the two filming styles (which is something that Peep Show makes use of a lot).
Hope that helps!