>One thing I didn't realize before I did all of this was how useless looking for a given shape is. Unless it is extremely flat, you are probably just looking for splashes of color. You would not believe the amount of color there is in the middle of a forest, or a field, etc, until you start looking for a particular color. Flowers, garbage, mottled sun, you can basically get any color you imagine out there.
Very true. This is the same sort of basic issue that a lot of optical illusions and magic tricks are based on. Human brains (and to some extent probably many animals in general) tend to out of necessity be a lot more sensitive to change vs static imagery and use a lot of processing shortcuts. There is so much data constantly coming in that processing all of it would be paralyzing, so a lot of the work really is throwing most of it out.
That's also why active signaling is so valuable in emergency situations. Even without touching on any sort of networked devices, tools like colored smoke flares, LED lamps/torches with a strobe feature, highly reflective metallized boPET (aka Mylar and other brands) flags or streamers light enough to have significant motion even in very minimal breeze, alarms, etc are all quite valuable because their dynamic and artificial nature makes them stand out more clearly from farther away. The problem comes with them needing at least some level of consciousness and ability to take action to deploy.
I do think there's more room still for innovation in safety equipment when it comes to automated emergency signal systems that can be linked to biomonitoring and thus respond automatically to signs of distress if the user doesn't cancel it after a given timeout. There are some products on the market right now, but the ones I'm aware of are purely electronic and depend on S&R having a receiver of the right type and/or on availability of network coverage. Satellite-based emergency signals don't seem to be practical or economic enough yet for ubiquitous usage. They both can still be incredibly valuable, but in addition it might be nice in some situations if automated deployment could be linked to non-electronic signals. For example, a compact self-contained system attachable to the top of a backpack with mylar balloon (possibly with a small strobing LED lamp), enough helium for auto-inflation, and a 100-200 ft tether that could be triggered automatically or manually. Standard mylar balloons can remain taut for a good 5 days and float for a couple weeks before losing too much lift, and the weight and cost of the basic components should be reasonable. While of limited use in certain environments like dense forest, in many areas it'd have no trouble reaching full extension. A floating bobbing reflective object (or at night lit by even a minimal LED) should be visible from a significant distance vs something on the ground but be safer and easier to deploy then trying to climb something to achieve vertical. Effective signal lifetime vs other consumables seems like it might be favorable as well. Or maybe there is something like this already?