Remote start video recording

Hi,

I want to use my phone on a helmet mount to record video while skiing and biking.

Since the phone is on top of the helmet i do not want to touch it.

Is there a way to remotely start recording?

With Siri? Have a shortcut to start recording but the phone needs to be unlocked. Is there a way to leave the phone unlocked?

Can I use an iWatch?

happy for any solution :)

best regards Per