Last year I upgraded my older X-10 devices to Kasa smart switches and plugs, and am very happy with the results. But I miss not being able to control my lights and devices using a variety of key fob remote controls or surface-mounted 2-, 4- or 6-gang wall switches.
Now that Kasa supports smart actions, allowing a smart switch to control other smart switches, plugs or groups, I can install a new smart switch and have it control any light or device already controlled by a smart switch or plug. But that requires a new work box and hot/neutral wires for the switch.
It would be great if TP-Link sold a thin, decora switch-sized, battery powered remote control smart switch.
Lutron sells such a switch (called a pico switch) for their Caseta line of smart switches. It's the size of a standard decora wall switch, but is very thin, and can either be used standalone (handheld or sitting on a table or desk), or it can be surface-mounted on a wall (no junction box required) with a standard decora switch cover, providing all the capabilities of a smart switch, but with no wiring required.
Imagine you have an overhead light in a room that's controlled by a single Kasa smart switch. You'd like to add a second wall switch on the other side of the room to control the light (basically a 3-way switch application). You can do that today with a standard Kasa smart switch, but that would still require new wiring and a new work box. With a new Kasa remote control smart switch you would simply mount the new remote control switch on the wall, and assign a smart action to the new switch (to have it control the other smart switch).
This new remote control smart switch would be battery powered (user replaceable) and thin enough to surface mount it on a wall with a standard decora switch cover (Lutron sells a special backing plate for mounting their pico switch on a wall). It would connect to your WiFi network the same as a standard Kasa switch. It would probably have separate on and off buttons, instead of the rocker switch used with the existing smart switches.
The challenges would be: 1) Fit the electronics into such a thin case, and 2) Provide sufficient battery life so the user isn't changing batteries frequently.