One of the features that I'm anxiously awaiting is dynamic homepoint on the Mavic Air so I can have the drone track me on my bike without having to lug the controller with me.  Currently Trace mode without the controller only works for 100 meters before the drone stops and hovers.  I understand that this feature was not present on the Pro or Spark at release, but came along in a firmware update some time later.  I've just purchased the Litchi app, and while I haven't played with it yet, it does seem to support dynamic homepoint for the Mavic Air.  How is this possible if it requires new firmware (at least for DJI GO4) to work.  Has anyone tried it out?

These features come with an update to the DJI Go app not a firmware upgrade. The Mavic Air has the capability of supporting dynamic homepoint, but the DJI Go app does not have it enabled (someone in DJI decided that this feature should be left out). Litchi on the other hand which uses the DJI SDK has access to all the features/modes that the SDK permits and as a result supports it.I have been trying Litch and follow me and Magic Leash and unfortunately I am not pleased with the results so far.

Please don't put the controller out of your hands while the drone moves autonomously.
For your safety, the safety of others and your mavic i would get another person involved that rides the bike and you shoot.
If you trust someone to fly your mavic you can swap...

The more interesting feature in litchi for you is magic leash.
You need another phone with the magic leash app and you can track the other phone with that.
But even then i really recommend keeping visual line of sight to the aircraft and stay put on your controls if gps malfunctions happen (never happened to me but you wanna be prepared).

Dynamic HP in Litchi and Go4 are differant.
In Litchi it uses the device location when set...
In Go 4 it uses the AC location when set...

But can you control the MA witch Litchi with NO RC?

Yeah its kind of sad that DJI app does not support what 3rd party software do.. Resetting your HP every 100 meters is anoying.