Some niche gadget-y things that are alive and well in the "a few hundred bucks or less" range:

* hardware tools / multi-tools

* bluetooth speakers

* portable projectors - outdoor big-screen movie night on the cheap

* the "sports/action" camera market - waterproof, magnetic/mountable, go-pro/insta360 etc

* pro/am mirrorless cameras are mostly too expensive to qualify but there's some really cool accesories now (handheld stabilizing gimbals, say)

* everything in the thread/zigbee/etc home automation space (sensors and buttons and automations...)

* car gadgets for enthusiast cars (things that plug into obd ports for diagnostics or real-time display of measurements), or "add android auto to your old car's built-in screen" multi-media retrofits (though in gaining things like this we've lost the ease of just things being single- or double-DIN in the first place), or dashcams

* vr headsets (feels very much like the sort of thing Radioshack of old would've been all over like the tiny handheld TVs)

* fitbits and such wearables

* portable monitors

* mechanical keyboards (as well as macro pads and such)

a lot of them qualify as "phone accesories" but I'm not sure that takes away from them

Half of those are basically just extensions of your phone. Just saying but I guess you are right gadgets have moved to be cell phone feature extenders.

Projectors and keyboards have both been around forever, I don't think most consider them gadgets but its a matter of opinion.