Phottix has introduced a new wireless triggering system called Laso which consists of a radio-enabled wireless trigger and receiver, both of which communicate using Canon's 2.4GHz radio standard.
That means you can use a mix of 600EX-RTs, 430EX III-RTs and older non-radio enabled EX flashes while controlling them all from the camera without the experiencing limitations of line-of-sight optical triggering.
You can even use the Phottix Laso Trigger in place of the more expensive Canon ST-E3-RT Speedlite Transmitter in an all-RT kit with full functionality.
B&H has the Phottix Laso Trigger and Laso Receiver available for preorder.