saliva, there are providers on TER who will tie you up and spit into your mouth.  It's kind of like water-boarding with saliva.   If you get a boner from saliva, this just might be your ultimate experience.  If you are not getting enough saliva, they switch to urine.  

 
With that said, you DO realize that there are gels that providers can put on their tongues before a BBBJ to seemingly increase the amount of saliva, don't you?  Is it real or is it Memorex?  You decide.