Music educator wants a better metronome

"I'm a musician and music educator.

I have always had a problem with metronomes. They are all basically the same and while they have received numerous improvements since their invention, I still feel they are behind the times. 

I have great need of a fully programmable metronome capable of running a very specific, possibly very long sequence of time signatures and speeds. The software would need to be able to switch between beat patterns at preselected intervals. I want to be able to customize a sequence long enough to cover an entire piece of music with irregular time signatures. It also needs to be able to simply start at one tempo and slowly rise to another over a variable amount of time.

For a stand alone device that does all this, and is able to plug into a speaker system, I would easily pay $100 and never look back. For a smartphone app, I'd pay several dollars, but would like very much like to try a free version first."