The mouse is more commonly swapped in situations with physical access. Without physical access, those non-BlueTooth wireless mice (with their own RF dongle) are vulnerable to remote keystroke injection.

Especially the pre-paired ones. I’m wary of older Logitech Unified dongles, but the newer Bolt platform offers a bit more comfort.

Hard part there is getting the wear and tear from oils in your hand to look identical.

Although maybe most people don't pay attention to that.

just put it inside the original keyboard

Pop and swap the keycaps

Dirty keys on a pristine keyboard is a dead giveaway.

The other thing that’s hard to get right is the weight.

Hard to find material in most things today to remove to even out the added weight of an implant.

Even better use esp long range and have a receiver device outside maybe powered via solar… connected to cell network… this way no additional networks exposed internally…

I mean... http://airdrivewifi.com/

https://shop.hak5.org/products/key-croc

Isn't it way easier to get a target to use a usb device than a keyboard

These days most keyboards are USB devices.

Yes but giving a keyboard as a present is more suspicious than just a harmless data cable.