I want a pedal that has two inputs, so I can mute one or both (basses), and I'd also like it to be a tuner.
Not that I've ever heard of. You can always run an A/B box into a BOSS TU-2, which acts as a mute and you could switch to either instrument before hand... or you could run an A/B into a Korg tuner, with a mute switch and do it that way... but I don't think there's a single monster to do what you're looking.
Just a stab in the dark/ No firsthand experience but I'm sure I read someobody here claiming a Bassbone offers more than one input. Don't know about tuner options. Then again- I could be wrong.
Raven Labs MDB-1 maybe http://www.gollihur.com/kkbass/raven.html I've just ordered a Radial JDV http://www.radialeng.com which has 2 switchable inputs. Plus it's the truest DI I've tried. neither have tuners though
Not being very helpful, since I dont remember the name or company, but I remember that there such a thing. It had at least two (but possibly more) inputs which could all be set to different output levels to balance out different instrument levels or different EQ spins, a tuner, and a few other little features. It was marketed towards more high-end touring acts, since they need things like that for all the guitars they have to set up. Try looking for touring equipment product lines.