Let's go hypothetical and pretend that your software startup was successful. Having accumulated some cash, you now have the resources to start something bigger -- potentially a startup involving hardware. How much money would one need to accumulate in order to have a serious chance at success?
More specifically, if one wanted to manufacture a next-generation Tablet PC (perhaps like the TechCrunch tablet, but not at the rock-bottom price point), how much capital would be necessary to bring a company into fruition to make/sell one?
My experience over the course of a couple of hardware startups doing more off-the-shelf approach is it would take you about $20-$35MM in total funding for a typical hardware startup doing something semi new/radical.
The hardware design itself can actually be relatively cheap. Packaging (custom tooling for cases, etc.) can easily cost you $20K-$300K (ie: as much as a big Angel round for some software startups). Manufacturing costs are usually a function of volume commitments and timing. So, you are going to be incented to commit to larger manufacturing runs than you are comfortable with to keep the per-unit cost low. Inevitably, after you do this you find there is some trivial but important item you missed, so you end up with re-work costs, or if you're very unlucky a lot of scrapped inventory.
To answer your Tablet PC question, my guess is that you're looking at $10M. There is not a lot of invention there. You'd pull together a lot of off-the-shelf components into a new form factor. Most of your early costs would be sucked up by the design and tooling of the casing and overall industrial design. I'd venture that you'd be $500K into it just for ID and an ME to layout the (presumably) injection molding designs for the case and first mold. Budget another $150K ish for UL and FCC certs (your outsourced factory can help you with a lot of this process). Then you're likely to go through probably $250K in the initial hardware designs and single-unit prototypes. You'll generally need or want 1 prototype for each developer (probably 5-8 in this case), plus another 6-12 for QA, and another dozen or so for demos and for employees to carry around and just "use" out in the wild. If you're making a tablet with an $800 price point, your production BOM is going to be around $200, and total manufacturing costs around $350ish, but your first prototypes will cost you $1000ish/ea at first because a lot of it will be work done by hand, etc.
So, thinking purely off the top of my head, you'd probably take a $1M angel round, a $4M A round and a $5M B round. Since this is a semi-proven CE device and not something radically new, you just need to build it and get it out there, not convince the world why they need it.