Ladder fall protection options
You ask about mitigating injury, but it seems feasible to implement preventative measures, first. The correct way to repair the siding is not with a ladder but with a boom lift or scaffolding. Doing so would avoid breaking 3 rules of ladder safety:


Maintaining 3 points of contact,
Not leaning to a side, and
Standing on platforms instead of rungs, which are designed only for ascending and descending.


These rules are intended to keep you from falling. I admit to breaking all of them, too, but in retrospect, my ladder-related accomplishments don't seem that important.

Assuming you still want to use a ladder, I suggest browsing the US OSHA rules on Personal fall protection systems. Note the 22 kN (5,000 pound) minimum breaking strength for the anchor, tether, and harness. Also note that belt-only harnesses are prohibited.

A complete fall protection kit will cost about $200 and are available for sale at many Websites. The most difficult part to find will be a suitable anchor. The most common anchors are intended for roofing and attach to the peak of the roof with 20-30 nails. Anchors are also available to mount to the top plate of a wall with 4 large bolts. A single eye bolt isn't strong enough to transfer that 22 kN to the frame of the house.