Control of DIY amps via phone

I searched awhile this for this but I would like to control my DIY system from my phone maybe via bluetooth (?) elementary stuff turn on and off equipment. Maybe a few other functions I haven't thought of yet. I have remote control on my dac that takes care of volume and streaming functionalities. I want something more flexible than just another remote control and use from single device. Any suggestions are appreciated.
Thanks.
 
A Raspberry Pi with a relay HAT connected to your home network would certainly allow you to turn amplifiers on and off. HATs with four relays cost well under $10. You would have different ways to remotely access the Raspberry Pi depending on what kind of phone you use (I hope is not a fruit).