Solaria's page

Complete Adventurer has alchemical capsules that can be disguised as teeth. Cost is 300g plus contents.

Alchemical Tooth:
Those relying on secrecy in the use of their alchemical capsules turn instead to the alchemical tooth. As its name suggests, this specially concealed item has been made to look like a tooth. The tooth functions in all respects like a capsule retainer (see above).
In addition, it is very hard to find without a thorough search (Search DC 30). The false tooth is most often used as a concealed version of a capsule retainer, but a few extremely dedicated spies and other agents carry a tooth filled with poison as insurance against being captured alive. An alchemical tooth can hold one dose of any contact poison or ingested poison, but such poison can only affect the wearer of the tooth—there’s no way to make the tooth an effective delivery mechanism when combined with a bite attack.

Careful about the immunity to morale effects...

That includes rage for those pondering bloodragers or barbarians.
Parts of bard songs and various spell effects (like bless!)

I kind of want to make a Ghoran Skald now. Bard/barbarian hybrid that makes everyone else rage, but can't themselves :P Whether the idea would work would be heavily dependent on party make up I guess.

Multiclass?

Does Mad Magic apply to spell-like abilities?