Sorry, I don't know how it works in Maemo, but not long ago I had a look at the code of LXDE's battery monitor. It relies indeed on virtual files provided by the kernel's acpi interface, and I guess that would be the most reasonable approach for any other battery monitor.
Unfortunately these pathes are hard-coded into LXDE's battery-monitor and I think it's the same for other monitors too. So you'd have to change the code and compile the monitor of your choice on your own instead of an easy way like just reassigning some environment variable.

btw: There is a way to export the battery status to the /sys filesystem if you use the power kernel, but I'd have to search for the link.