Network-compatible power sockets are a good choice to reduce the support of your system. About the GSM (mobile), network (LAN) or internet (WWW), the socket can be switched. To powercycle is very easy with this hardware.
Watchdog is often supported. The watchdog automatically restarts your equipment as soon as they are no longer accessible on the network.
DIY circuit with Raspberry Pi and FHEM are to build for much less than 50 euros. With the search words “Raspberry Pi and power socket” and maybe “FHEM” to quickly find many tutorials on the subject on the Internet.
Professional providers of beautiful solutions are, for example: