Best "app" for Dojo - timer, training, workout, warmup, etc.

We have TVs in our Dojo. I want to setup a small device (permanently) so that we can use it for training, randori, warmup, etc. I tried amazon firestick, I could not find any decent app beside very generic timer.

Is there such an app?

I need this to be very simple. Some of our sensei are not too technical, having to browse a website from a fire stick is a no go for example.

I'm open to buy whatever device/hardware is required. just need the right thing. I'm starting to wonder that such a thing/app does not exist!

thanks in advance. if that does not exist, I'll try to develop one in my spare time in the next few weeks.