By "high current" I mean relative to the standard ARM pins which are pathetic 
+-25mA on those 16 IO pins.
The battery is just a coin cell and only for backup. There is a connector that allows a larger battery to be used but once again just for backup. That said you can just use a battery instead of a PSU. I could modify things to allow the charging circuit to charge a main battery as well.
Also the on-board PSU can be bypassed with a plug-in module, so that feature could be used to provide a supply from any battery even if a boost regulator was needed.
it would probably be quite expensive
Possibly, certainly more than a standard Arduino but OTOH if you look at what people like Olimex can produce, their Duinomite-MEGA for $29 then there is hope that this can be done for a good price as well. Also maybe variations can be made as not everyone will need all features. For example the LCD doesn't have to be loaded.
the Pi really isn't in competition with this with only 8(?) IOs..
Different horses I guess, this board is all about IO and expandability, not about user interfaces or UNIX.
Rob