Here's another option
I use LoopBe30 for internal MIDI routing. MIDI Yoke would work too.

Pick up midiOUT VST
http://www.thepiz.org/plugins/?p=midiOut

Add to a plug in on an extra midi track you're not using, For example the "Soloist" track.

Set midiOUT to say "01: Internal MIDI"

Turn on the Conductor, "Enable control by Midi keyboard"
Set the MIDI in of Band in the Box to "01: Internal MIDI"
Yes, the same as Midi out from the soloist track.

Notes you add to Soloist track will control the Conductor.

Add some C4 notes to the soloist track over the measures you want to increase tempo.

Each time a C4 plays the tempo will increase by 1

This a very interesting way to add a "control" track to BAIB. Pick "Show MIDI notes" in the Conductor to see all the options.