Wireless button for Arduino

Is there any wireless button I can use with Arduino? Something with a battery, and when you press the button the Arduino can read it as analog input. And if not, what is the smallest device I can put together in order to give a signal to Arduino from a wireless button?

Thank you.

There are (too) many options.
Something with a small battery could be an existing remote control. If you put that in a large button, then you can connect the receiver to an Arduino.
In Europe the 433MHz is legal, in the US the 315MHz is used. Check what is legal in your country before buying it.

Keyfob : https://www.adafruit.com/product/1095
Would the circuit board of the keyfob fit into this button ? https://www.adafruit.com/product/1190

Can you tell what it is for ? What is your project about ? How reliable should it be ? What is the distance ?

There are numerous variations on this tech: