The FLEX-6000 Signature Series SDRs have a remote power on contact that will allow you to power on and off the radio using a contact to ground connection (please see the FLEX-6000 Hardware Guide for more details).
The ability to turn on or off your radio while operating remotely is a necessary convenience. One way to do this is by using a Internet controlled switch. Below are a few third-party devices that our users have successfully utilized for turning on and off their radios using an Internet connection.
There is a very good Community topic on this issue too
Note: FlexRadio does not recommend or endorse and of the specific products mentioned above. They have been successfully used by FLEX-6000 owners and are listed here for your convenience and information.