Funny, I just found both of those devices today after doing more searching (like 4 hours worth!). The shutdown controller looks very promising but does not include power supply switching. The OpenUPS really looks like a slam dunk, although it's hard to tell whether that one or the picoUPS or DC DC converter (in UPS mode) is the best choice. At first glance the OpenUPS with a custom battery appears to be the best because it handles shutdown as well as telling the PC that it's running on battery which is convenient. I have an email into their support center asking which product to use.
I'll post back here with my findings as this seems like a very useful arrow to have in the quivver.
