I created this thread to collect hacks that are being looked into by their owners. I will start with the two I have found so far. Add those you come across and we can discuss them.

Here is one hack in which the owner is wondering whether he can control a robotic arm with his S1 through the PWM ports.

Hello and good day rhoude57 - YUL. Thank you for creating this thread. I hope this thread will get a lot of replies with regards to this matter and thank you for your support.

In this RM S1 hack, it's owner designed a 3D printed Forklift powered and controlled through the PWM ports. The designer has not yet published his design of the components, assembly instructions and programming (although a Scratch program is shown in the comments as a Custom Skill.
RoboMaster S1 3D Printed Forklift Hack
NOTE: The "Officiel DJI RoboMaster S1 Owner's Group" is a closed group, but I suspect strongly that everyone in this forum is eligible for membership, or perhaps are already members of the Group.

Cool video!