I think the PenPal interfaces with the port on the epl1/ep2/epl2.
I'm wondering why people wouldn't just use an Eye-Fi card ?
Sure you can't connect to a device direct (Eye-Fi relies on having a Wi-Fi access point) but the throughput is significantly better, the function doesn't use the hot-shoe, its not vendor-specific and you can also get portable AP's (or hack a device to appear as an AP).
my hope is that the bluetooth stack also allows for remote functions since the EPL-1 was crippled for remotes. It would be nice to use my laptop or smartphone to do anything from a remote snapshot to timelapse and astrophotography.
And although I would not use this to transfer files all that much, I can see why people would rather keep their high-speed high-capacity cards. But you are right, if people are concerned with nothing but transferring files, eye-fi is much faster than bluetooth.
The Pen Pal will not work on any camera that comes before the E-PL2. The E-PL2 sports a new accessory port 2, labeled with 'AP2'. Neither the E-PL1 or E-P2 will interface with the PP for the purposes of transferring files, since this device had not probably been conceived of when those cameras were designed.
On the bright side the pen pal is the only new accessory that appears to be E-PL2 only.