hearing device called an IntelliEAR since I was suffering from wax in my ear. It worked better than I expexted and was very sensitive. My Dad had used it to listen to TV.
After I got my GOPRO I was dissapointed with the sound so remembering this device I pulled it out . I took a skeliton case I use for dry normal work and drilled a small hole over the mike area and stuck in the niple of the hearing device. The sound is fantastic. This IntelliEAR cost from $16 to $25. Be sure to get the rechargable one not the battery one. It lasts 2 or 3 hours on one charge. I t has a volume controll and I had to turn it down since it will pick up even the slightest sound . I put a piece of foam over the mike end. I now am experimenting with a 1/4" plastic tubing that gives me the ability to place the mike up to 10' feet away from the camera (for the fun of it) Look up INTELLIEAR.com There are about 10 models on the market now so the picture I'll show you is my older one.