I like a count in to start the song (click or visual) to anchor myself in the tempo. Currently I am doing this by starting the tracks on the second measure but that seems less ideal. I'd prefer to just have a configurable beat count-in that is not part of the actual arrangement.
A while ago I used a line 6 product, I think it was called Rifftacker, that had a cool feature where you shanked the guitar for 4 beats and it interpreted the input as tempo and also started the song. That seemed like the most natural way to both start and set tempo that I've seen thus far. I think it also had an arm mode too to start recording.