We know what you are thinking: the computer, phone or tablet you are using to read this article already has a calculator and a whole lot more besides, so why do you need an old clunky one on your desk?

It seems Canon think that too, but rather than suggest you use the one on your PC, they've got a different idea.

The Canon X Mark I Mouse, you see, isn't just a mouse, but a mouse with a built-in personal calculator that also acts as a wireless laser mouse and numeric keypad for personal computers. Wow.

Coming with Bluetooth 2.0 connectivity built in, three click buttons and a scroll-wheel, the calculator can be used as a mouse, or a calculator from the same device, says Canon.

The X Mark I Mouse can also be user-locked to avoid accidental pressing during "mouse" use. Phew. 

A high-resolution, ten-digit display panel ensures that data is clearly displayed at all times, letting you write endless 55378008 jokes and provides at-a-glance updates on the operational status.

The X Mark I Mouse is available from November 2010, priced at £39.99