What I'm trying to find is a hard drive interface. Preferably SATA if it exists, or USB if not. I want to mount a second hard drive internally in my laptop. There's no extra bay to install one the "normal" way, but there's a free Mini PCIe slot and a huge open space under the bottom cover waiting to be hacked.
I don't think one exist. but the mini-PICe is capable of steaming USB data accross it's connector. So it is posible for someone to build a mini-PCI to HDD via USB to HDD interfaceing. That would mean thay could make a mini-PCI to EIDE or SATA. Only problem is there is not a power output in the mini-PCI connector to supply the needed voltage for the hard drive. And without many notebook PC's having enough space the entire idea is not worth any manufacturers time or money.
Basicly, as long as the power of the device does not require more than a single 3.3V than anythin that they already make as a PCIe for desktops or anything USB, they can make it into a mini-PCIe as long as physical size of chips and components fit.
Products known to exist in mini-PCIe:
WLAN (Wi-Fi a/b/g/n)
WWAN (cellular air cards)
Memory boosters (Intell)
Solid State Disk (SSD) Drives
TV/FM tuner Cards