This is an appeal to those DIYers and other talented hands-on types out there:

It would be great to have a switchable input for my portable amp and/or iems directly such that when the phone rings or wife comes into my home office to talk I don't have to pull one or both earphones out but rather could switch to a small microphone/room monitor that would feed the caller/wife's sound into the earphones. So what's needed is a little device with switch that doesn't degrade the music source input but has a mike that can be switched in to hear outside sound--either instead of the music or on top of it.

Would any of you know of something suitable or be interested in devising and making one?