Cron is not part of Fedora Silverblue (as well as Atomic Host). You can install (overlay) it with rpm-ostree. But it is better to avoid as much as possible to overlay packages in such systems. So, how to take advantage of systemd instead of cron?

How to use the camera module on a Raspberry Pi 3 running Fedora 29?

LibreOffice Impress, has a feature useful to switch presentation slides using an Android app. It is a very nice feature, but the last time I used it (on version 5) it was a little unreliable.

So, what about an handmade solution? Just for fun. You need a micro:bit and a Linux (Fedora) workstation (equipped with Bluetooth).