See http://www.mythtv.org/wiki/Sony_PS3_BD_Remote#Alternative_Methods. I've been using bdremoted for over a year and it worked perfectly, the latest Python update though made it stop working so I'm now trying to make it work again with the newer method.
Also of interest
As of this writing, the best way to enable the remote for use with Myth is to patch bluez. A default installation of bluez will enable the remote, once paired, as a faked modifykeyboard but produce scancodes above 255 which require XInput 2 (Xorg 1.7) AND support in the application (MythTV and any player to be used). Upstream bluez won't integrate the patch since the XInput 2 way is preferable.
A problem of this method is MythTV key mappings might require tweaking since each remote key is mapped to a scancode, it maps to key instead of a character (two characters on the same key are equivalent).
Thread: http://forum.xbmc.org/showthread.php?t=50717
Relevant posts:
Last patch known: http://kitlaan.twinaxis.com/holdingcell/bluez_ps3remote.diff Tested against bluez 4.60
References: