It depends on what kind of connectivity do you need, and how fault tolerant you have to be.
If you need mostly wifi/bluetooth, there's a very nice line of microcontrollers: ESP32. They have a lot of variants, so you can find the one you want.
If you need IO pins, Arduino is the way to go. They too have lots of variants, with more pins, less pins, large, small, and they are very easy to program.
If you need processing power, the RasPi variants are the ones you should use. They run Linux, they have beefy processors (for an embedded platform), lots of RAM, and are accessible too.
STM have some industrial-grade microcontrollers too, and I believe you can program them with C. I have a STM Discovery in a drawer somewhere...
Fault tolerance can be achieved using more than one board, and depending on the equipment you are controlling, you can use some combination of OR-gates or counters to define if you are activating it or not. As the boards are cheap, it won't be much expensive having 4 Arduinos giving the same input.