How much money would it take to get into hardware?
graemeklass: The major costs would be the assorted tooling charges:
- plastic moulds: for a tablet size probably $50-70k. I would recommend you get an experienced industrial designer to guide you through this process. Make sure if you get quotes from China that you don't give the 3D model for the quote - give 2D technical drawings with enough information for a quote but not for full production (your industrial designer should know this). 
- PCB boards: nowadays tooling charges are quite low. We use OurPCB.com for a smallest circuit board and the tooling charge is in the low hundreds. We source the important components and get them to ship it to the PCB makers. they then send the completed PCB's to us.
- packaging: allocatae a few thousand to set up your box or plastic packaging.Stage your production:
- pilot run (say 10 PCB boards to get all of your component logistics sorted out).
 - 1st run (100 PCB's with 100 plastic shells and packaging)
- production run (1000 PCBs, 1000 plastic shells and packaging)Assemble, program and test your devices close to you (ie. your garage :). This allows you a) to keep your IP close to you and b) iron out any production bugs, processes etc. so you are ready to outsource the whole production and assembly (if you so wish).