Yes ... they seem to heal undead.
Which has me thinking...
When I saw how overpowered the Blackguard summon was, I tried making a high level shadowdancer, to see if their summon was equally uber. (Blackguards can basically run around and level up doing nothing but healing their succy, while letting it do all the work)
It wasn't -- it had no real AB or AC, in fact it was basically useless against anything that had immunity to Lvl/Ability drain. It also couldn't be healed, so didn't last long (...giving it a resto pot would kill it. Giving it one of those Death Pots would kill me, )
Maybe there's a market out there for Severed Heads among the disheartened Shadowdancer community?