Put the sensor in the space you are trying to light, and suddenly this "common need" becomes "not a need at all" which is why you can't find them, since that's how it's done, when done conventionally.
Either move the switch into the room or get a remote sensor switch and put the sensor in the room.
First let me just say, that I noticed that you did not ask, How do I stop a dimmer switch from humming?, but rather WHY is it buzzing (especially, here- not there).
Essentially, your dimmer is also creating or acting like a speaker, because it is physically causing air to vibrate, which is detected by your ear... in other words, sound is created by moving air back and forth. A speaker is made by inducing a magnetic field in an object (like a coil or a bulb filament) which exerts a physical force upon the (induced) object causing it to move and by default, move the air. The range of human hearing is 20 to 20,000 Hz and the frequency of the electricity in a residence is 60 Hz.
The reason it is happening in the dimmer is the same reason as the light bulb; some piece of the dimmer or a neighboring conductor is physically vibrating.
Why it is only in the one spot has to do with something called harmonics... and there is a long physics lecture involved. But in short, harmonic distortions happen because like-waves are additive, meaning that electric wave of similar frequecies (and amplitudes) will add together. The light bulb in the bedroom (or perhaps of the fan motor) and the dimmer are acting like tuning forks each causing amplification (or resonance of waves) in each other and the result is induced power which is strong enough to cause physical movements, and thus, audible feedback.
Of course, from the other discussion about how to stop it, the answer was to change the bulb (that's acting like a tuning fork- not mentioned).
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That is totally fine. NEC requires receptacles be at a certain spacing (so extension cords are not needed). It does not care if those receptacles are split and half controlled by a light switch.
If anything, split receptacles all around help avoid the need for extension cords. I see many homes where the solitary split receptacle is stupidly placed, and you are stuck with a bad placement, or must run an extension cord.
You need to be very careful with splitting receptacles. You must break off the correct tabs. If you fail to break off a tab that needed to be broken, you will cross circuits into each other, defeat light switches, or make a rather big bang if it's an MWBC. If you break off one too many tabs, one outlet won't work. If it's getting confusing, then break off both tabs and pigtail both sides of the receptacle, and hook them up as if they are 2 separate receptacles, one at a time.
If another bedroom has 2 complete circuits for bedroom receptacles, that is fine. It would be rather unusual to see a receptacle split between two different circuits, but this is a rarely-seen feature, not a bug.
It's also possible that a duplex receptacle, or even a receptacle chain, could be fed by a multi-wire branch circuit. This carries 2 full circuits on a single /3 cable (black red white). These are very efficient ways to bring a lot of power to a room, if you know what you're doing. If you don't, you can inadvertently create a serious hazard. This MWBC solution would not be used in new work, because it makes AFCI and GFCI protection more expensive, it is cheaper to simply run two separate /2 cables.