Enabling the use of Magic Trackpad/Mouse for "hold"-inputs

I would like to define "hold"-related actions for my trackpad and magic mouse. Specifically, I would like to use it to e.g., scroll through a timeline in Final Cut Pro/Logic Pro/etc. I would like to define a "gesture" that is triggered when a second finger touches the device (like a tip-tap) but only when it remains on the pad. I would like another trigger when the second finger is lifted. Further, I would like to query the distance between those two fingers (to change the scroll speed) and have another trigger when that distance changes.

I know this is a lot, but I think it would enable many really cool use cases (basically fully free "chords" on the trackpad and magic mouse).

I am happy to discuss this more and provide more details on what I have in mind.