You'll need:
An Android phone using the MSM72K USB chipset (so, the desire, Nexus 1, Deam, Evo 4G, etc.)
Root access
A CUSTOM Kernel with the correct modifications
Terminal emulator
Now, the problem is the "custom Kernel" bit. HTC hasn't released the source for the Kernel in sense 2.2, so that rules out all 2.2 sense Roms. However, we DO have kernels for everything else. That includes Sense 2.1 and non-sense Roms.
The next catch is the kernel needs to be customised for this, which means the Rom itself will have an impact on this. Some roms use custom Kernels and the Kernel will need to be compiled specifically for that ROM. The side effect of this is that you'll lose all USB functionality of the phone. So no wired tethering, no adb, no mass storage connection, no HTC sync. Charging will probably still work though. There are workarounds to all of these things (Wireless tethering, wireless adb, one of the many file managers with network share support).
Then, the operation will be simple. On your phone, you'll open up your terminal emulator and type psfreedom_desire.sh or something, turn on your PS3 and press the eject button, then away you go. From my understanding, after the PS3 has been jailbroken and you've got Backup Manager installed or whatever, you can remove the USB cable and still continue to use it, but the next time you turn on the PS3, you'll need to jailbreak it again. For the moment at least.
But, that's down the line, right now, the code needs to be written by greater people than I, so lets just wait.
Lo malo que perderemos la funcionalidad del USB con el kernell modificado.... menos cargar la batería.
Supongo que esto lo irán puliendo con el tiempo...