Tron,
You might want to check Circuit Cellar: www.circuitcellar.com and www.micromint.com. Back when CC was in the old Byte mag, Steve Ciarcia (sp?) used to have a lot of SBC projects. Seems to me that just after they became Circuit Cellar Ink (c. 1985), they had a "Data Logger" designed for remote location monitoring. An updated version might be ideal.

As far as battery power goes, the biggest load will be the HD motor. If you wrote to some sort of non-voliatle RAM disk, your power requirments drop pretty quickly. I think CCI had a lot of those type of circuits, too.

Thorn