How can I make a wireless sign that lights up with a button?

Do you really need it to be 'smart'? You might be overcomplicating things. Automatic lights that adjust based on time of day could be more efficient. If the rooms are regularly booked, you could set the lights to follow a cycle. But remember, if you want to keep it simple, a physical switch is always reliable. Just be clear on your budget first.

A simpler solution might be to set up a remote control outlet switch with a light. You could use translucent material to write your message and put a light behind it, so when the light is on, it illuminates the sign to show the remaining time.

It really depends on how much you can spend. You could purchase an inexpensive light and create a simple sign below it saying '15 mins left' when the light is on. This could work with minimal requirements. Just remember that if you're going into more complex setups, like wiring, that could increase costs.

If you're looking for budget-friendly options, you can also check out books in your library that cover 3D printing or electronics. They might have similar projects that could give you solid tips to work from.

One option is to use smart bulbs that can be controlled from your phone. You could hook these up to a device like a Raspberry Pi, which lives in the button box connected to the internet. That way, when the button is pressed, the bulb lights up! Just keep in mind, if you need it to run on batteries, using an ESP32 might be a better choice instead of the Raspberry Pi.