Space-time.
When we recently reviewed the G-Shock GPW 2000 Gravity Master watch, the toughest task we set it too was sitting on one our wrists in a coffee shop. However, G-Shock themselves decided to demonstrate just how hard-as-nails the time piece actually is by sending it into space... and back. Launched from our own home county of Yorkshire, the watch was attached to a weather balloon and sent up as high as it could possibly go, to then plummet back to the earth.
The balloon and watch ascended to a height of 44.1km (27.4 miles) before bursting. That is, apparently, the highest a balloon of that type has ever gone, passing beyond the 'Armstrong Limit' at which point human blood boils. The temperature up there was -58 degrees Celsius, with an atmospheric pressure of just 0.00146 bar.
After floating back to earth, the watch was then given an extra test by being released at 123 metres, free-falling all the way to the ground and still surviving to function perfectly. The above video is pretty cool as you can actually see how long it takes to gently rise up to the edge of space, as the hands tick happily away in the hostile upper atmosphere.
Nice to know that, if we were taking a trip into space, the Gravity Master is the watch to take.