Controlling the Sony A7 III with the Ronin-S
Although the Sony A7 III isn't yet fully compatible with the Ronin-S and it's focus wheel DJI have included an IR remote cable. The cable simply connects to one of the Ronin-S accessory ports and then as with any other IR remote can be used to start and stop recording.
Get the Ronin-S in the UK: https://amzn.to/2HpsfEd
Get the Ronin-S in the US: https://amzn.to/2VlNVWD