I'd love to have a small, unobtrusive amp that would increase my volume just enough to be heard in settings like jams where there are often 5 or more instruments playing with only one person singing.   In that type of setting I often have trouble catching all the lyrics even when the singer has a big voice, so with my relative lack of (vocal) belting power it would be great to have something that would make me audible.   It would need to have a lapel mic, because something as in-your-face as a mic stand mic or even a headset would be a distraction.   I think with a lapel mic, since my amplified voice wouldn't be any louder than many others' unamplified voices, this kind of set up would hardly be noticeable.

As for the amp and speaker, I'm thinking something sort of like a very small radio.   Radio Shack used to sell something like this, where you had a location on the dial that was your "station."   In a rehab center, e.g., you could sing into the wireless mic for this system and people in their rooms could hear you just by turning to your number on the dial.

Has anyone ever used something like this?

Genie