I'd like to have continuous control of the project BPM. It would ideally work similar to the rate slider or maybe a slider/knob could appear once you right click on the BPM. [all optional of course] Unless, there's already a way to do this that I don't know about...

Show the Master Track in the timeline, enable an envelope to control BPM (Tempo Map). Easy. D

If you show the master track and the tempo map envelope, set the pref :editing behavior -> mouse -> clicking an envelope segment edits the envelope", then you can slide the whole tempo map envelope (which will just be a straight line if the project has no tempo changes) up and down.

Thanks guys, I will try playing with the tempo envelope (it is a bit of workaround for immediate use though)

Another option? 

Liquidclear: Not exactly what you're asking for, but did you know you can tap in the tempo by clicking (in time) on the word "BPM"? You can bind it to a keyboard key as well.

SWS: Thanks for the tap tempo tip - that'll come in handy for sure :) As for my original request, I basically just would like a slider to control bpm in the same way we have a slider to control rate. (but now that I think of it, we have a right click function on rate to adjust rate to tempo)

anyone know how to get a learnable controller button to tap the bpm? i found this its just named funny (transport tap) thanks: also i cant figure out how to 'bind a key' i assume a keyboard key, to bpm, that would do well enough if i had to