I designed a simple "M4 receiver backpack" that uses a DC-DC step-up converter to ensure a 5V power for the M4 receiver module. The board supports 2 different kinds of converters, one from ebay (red in the photo below), the other from tindie (made by BBtech, black in the photo).
The backpack can be used, by default, without the step-up converter if the voltage is steady at around 5V. (A trace-jumper must be cut when a converter is added.)
The assembled board wired to Wise Clock 4 is shown in the photos below. Note that only 3 out of 4 buttons on the remote have a function on the clock. Each button press could light up a (optional) LED on the receiver board for visual confirmation.
A new design of the Wise Clock 4 board should probably feature a header for plugging in the receiver module, otherwise the back of the board will show a bunch of ugly wires.
This M4 receiver backpack could be used for adding remote control to other devices with buttons, especially when these buttons are hard to access (due to enclosure design constraints), or hidden (for aesthetic purpose). One example that comes to mind is an oscilloscope clock fully enclosed in transparent acrylic; drilling holes for the buttons would require some design stretches.
Schematic and board layout are shown below.
The M4 receiver backpack would be also suitable for hacking old commercial alarm clocks. Please let me know if anyone is interested :)