The”MPH Firmware launcher”allows to launch a firmware from the PSP’s memory stick. The firmware must be in file format and not in eboot.pbp format, for convert a firmware eboot.pbp in file, use the psardump02a tool. Use the tool at own risk! Release notes:

The firmware launcher shows now the browser (firmware 2.50 only) and he is more stable with video playing (firmware 2.00 only), see readme for all modifications. Source available.