BLEnky (on github) aims to make Bluetooth Low Energy accessible to the masses, even without any programming skills.

It is a firmware for cheap nRF51/52 based boards that is able to act as a binary sensor / actor with just a miniscule amount of configuration!
Expanding on that, more complex gpio-centric tasks can be realized woth it's own programming language, gpioASM (also on github).

Personally, I am controlling water boilers, door locks, fingerprint readers and building cycling sensors, game controllers, presentation remotes, motion/pressure sensors, airtags and much more with all the same firmware and just a coin cell!