Standard IEMs isolate you from the world, which is the opposite of what a hearing aid does. However, a specific category called "Active Ambient" IEMs bridges this gap. These are IEMs with embedded high-fidelity microphones on the outer shell. They pick up the sound of the room (bandmates, crowd, conductor), amplify it, and blend it with your monitor mix. The accompanying bodypack or app often includes a multi-band EQ and Limiter. You can boost specific frequencies where you have hearing loss (e.g., boosting highs to hear cymbals or speech clearly) and set a volume ceiling to protect your remaining hearing. I have no ownership/sponsorship in the product, but I personally LOVE the ASI Audio 3DME (powered by Sensaphonics), which is the industry standard for this. [1] It allows you to use an app to shape the ambient sound to your hearing needs.
The Pros: It provides hearing protection + monitoring + hearing enhancement in one device.
The Cons (Why they aren't daily hearing aids):
1) Form Factor: You are tethered to a belt pack. You likely won't wear a wired bodypack to a grocery store or dinner party.
2) Social Barrier: Wearing full-shell custom IEMs creates a "do not disturb" look that discourages conversation in social settings. This can be more socially alienating than a comparatively inconspicuous hearing aid.
3) Battery Life: IEM systems typically last 6–8 hours, whereas hearing aid batteries can last days or weeks.
[1] https://www.sensaphonics.com/products/3dme-custom-tour-gen2-...