metsfan - what distro are you using? The barry project bcharge tarball includes a udev script that works perfectly on my Fedora Core system; it launches bcharge when the Pearl is plugged in and does it's thing. I did have to reboot though for it to be recognized - I'm not very familiar with udev to know how to do a runtime reload (or even if it's possible).
My bcharge RPM is at home to look for certain, but I think it goes into /etc/udev/rules.d/ and was a simple 1-liner; note my patch above patches that udev rule to support the Pearl (product = 0x0006). It works regardless of mass storage mode setting, as it's based on the RIM product simply showing up on the bus (lsusb -v).