I have to cobble up a solution, too - but having been immersed in audio and being no stranger to the physics involved (and enough of: how the ear ackshully 'hears' stuff / what it means when the teeny cilia have broken-off, etc.) --
I'm still 'innovating'.
As I see it: the absurd prices for clever on-the-fly compensation are determined by
A) the vanity factor: make it too-small (imagining you can somehow get around the physics, spacing, separation of mic/'speaker' and physiology) and
B) the White-coat + 'mysterious' (to most) techno 'instruments, and the patter which capitalizes [literally] upon the ignorance factor; the unawareness of how such audio manipulation is today dirt-cheap.. if it's in a small box and not crammed into a vitamin pill that disappears into the ear canal.
I'm still evaluating (casually.. did I mention I'm lazy about research 'projects'?) what I might do with some bargain-steal close-outs of a half-cigarette-pack sized light-plastic box with an actually decent amp, 3 sliders for a crude filter-set - and how, practically - to do much more than the simple filters installed.
(I have some spares, should you want to play, too..)
My next stage would be evaluating the numerous Bluetooth or similar high-quality (ie near-flat actual SPL-response) over-ear speaker/transducer gadgets, though I'd not mind a small wire - depending on all factors.
Some minor factoids, theoretical and as verified-by-ear..
1) You need more than one 'program' - for hearing an orchestra VS ordering a Czechvar in a Coors hangout.
2) The problem is finding the design work already done, but not ultra-miniaturized. A digital controller would make n-programs an instant matter, permit cute things with those clever filters with steep sides.. to tailor for a variety of environmental situations. As with those other omnipresent 'programmable' boxes - the interface! determines just how much whiz-bang cleverness you can first arrive at through personal experiment.. then sanely control, on-the-fly.
3) The ACID test of any 'solution', as regards speech is ever: the Sibilants; you need to hear someone speaking all those intermingled ff's, ss's, ph's and particularly th's! Before/After - with great concentration. Somehow you have to restore.?. a bit of the 2000 - 4000 Hz response (and of course - perpetually stay Way-away from landing jets and Acid Rock-halls..) There aren't many of those critical teensy hairs left in the cochlea area: no amount of AMPlification can wiggle a cilium that's departed for other dimensions.
But my approach is irrelevant - if you want this thing to be near-invisible.
Vanity costs not only $$ but severe compromises in achievable audio performance and your ability to have that flexible control in a form YOU can Access (not via jeweller's screwdriver or magic boxes owned by the Vendor. Hmmm Windoze again.)
I gauge my hearing delta-% via merely cupping hands behind ears:
the noted difference is as good as a Fourier analyzer! if one has some idea of what happens in what octaves of speech, music (sirens, etc.)
Astounding how much $$ can be extracted to get.. not much more improvement than this simple test. Of course, this level Can be improved upon - but I don't believe (yet) that any of the teeny gadgets can come close to what could be done cheaper-while-larger.
I'll find out. Alas too.. while the $$ remains absurd - there seems little actual competition, probably because of the white-coat syndrome, a plethora of small vendors hawking SMALL items.. pretty similarly limited - and the fact that most people are too lazy to find out even a little about the elements of the Problem / and the means for addressing (at least many..) of the underachieving body-parts.
As one who despises Hype at any intensity.. I was prepared for the above marketing - but even with a local ~ept guy with some fancy equipment: wasn't prepared for the lack of candor about the actual limitations of (and my brief right-there tests of) even the high-priced spread.
It's as if all these guys have tacitly agreed that we shall all settle for a really bitchin 4-cylinder side-valve with chrome valve-cover: ie. it's as if Redmond had fucked this industry exactly the way it lies to itself.
(So even if I had a free-pass for one of these Ferraris with a '47 Plymouth engine.. I'd demur. Guess it's a curse, knowin even a little-Shit -- immersed in a culture that prides itself on wishful dumbth.) Oh well..
Rotsa ruck in the 'auditions', though - maybe I lied, and you'll find something that will -Suddenly- let you hear that triangle! in Petrouchka, the crystal purity of Sergei Nakariakov's pianissimo high-G or even.. hear the rain, again.
Ashton
:opTy