In reply to beefy_legacy:
There's a bunch of free timer apps that would be easy to use for a fingerboard session.
Best ones I've found are:
Hybrid Interval timer is easy to use and easy to add large number of sets.
New Interval timer is a bit more sophisticated - better suited to a whole workout. It also keeps a record of workouts you've done.
There's also one called Tabata. It's been on my tablet a while now but not really used it yet.
With all these you can create and save different workouts and then use them when you want.
Post edited at 12:39