Skype founder Niklas Zennstrom’s new FreedomPop project was initially shrouded in secrecy, but they’ve recently become a bit more talkative about how the company plans to offer “free wireless broadband” to their customers.

FreedomPop VP of Marketing Tony Miller spilled the beans about the company’s WiMax-based freemium wireless data service to Forbes, but left yet another question unanswered — what’s the “innovative” new wireless device they’ve got in the works?

Well, according to a high-level source inside FreedomPop, it’s an iPhone 4/4S case… with an integrated WiMax radio. Think of it as a mobile hotspot squeezed into a case — I’m told that it’ll run for up to 30 hours, and can share its Internet connection with up to eight devices (including the iPhone that it’s attached).

As I understand it, each FreedomPop iPhone case user will have free access to a 1GB data plan right off the bat. That’s the only plan that FreedomPop will offer for the sleeve, though their overage fees seem strangely familiar: each MB over the limit will cost a penny, which means every gigabyte over the limit is $10. That’s not to say that FreedomPop users can ditch their carriers entirely — the case alone isn’t enough to let users place voice calls, and major carriers generally won’t let you buy a smartphone without a data plan to go with it.

There are still some costs involved though, specifically a deposit that each user has to shell out for a WiMax-friendly iPhone case of their own. My source tells me that the deposit will be under $100, and will be fully refundable to customers if they ever choose to discontinue their service so long as the sleeve is still in good condition.

Users will also be running on ClearWire’s 4G network, and while that isn’t as fast as AT&T or Verizon LTE, it’s often more than enough to give 3G networks a run for their money (depending on their location, anyway). Their reliance on ClearWire could prove to be a bit of a stumbling block since it doesn’t have the biggest footprint, but FreedomPop is currently in talks with other “major” wireless providers about the possibility of branching out.

FreedomPop isn’t doing this out of the goodness of their hearts — they’re obviously in it for some cold, hard cash. Their plan is to make money off of a slew of value-added services they intend to roll out in coming months — it’s their hope that they’ll be able to convert 10-15% of their free users into paying customers, which will subsidize the service for everyone else. Whether or not that actually pans out is another question entirely, but we’ll have to wait and see how much momentum FreedomPop will be able to build first.

As far as how innovative this thing is, well, that’s debatable. It’s a concept that we’ve seen pop up a few times in the past, perhaps most notably when Sprint started offering the ZTE Peel, an add-on for the iPod Touch that gave the device a persistent wireless Internet connection. But hey, free Internet thanks to some low-cost, low-risk hardware? Giddy up.