I propose...

...creating a new international standard metre measurement. The international standard used to be represented as a bar (an alloy of iridium and platinum), held at the International Bureau of Weights and Measurements in Sevres, France. This standard was then replaced in the 1960s by a calculation based on the distance travelled by light in a prescribed time - a calculation designed to deliver the same measurement. 

For the new standard, I'll estimate what I think is a metre, then create a representation of it. This representation will be created out of a block of unstable material - this material could be fruit flavoured jelly, but made in a higher, thicker concentration than when its made for consumption. 

The block will be presented in a display cabinet set upon an unstable floor - such as loose floorboards or, if the exhibition space has a solid concrete floor, then the cabinet could be set upon a set of large flat boards which are laid over a number of uneven planks. Either way, the area of the unstable boards would be large enough to ensure that any viewer wanting closer inspection of the metre bar will cause small vibrations, effecting the stability of the bar.   

I may apply to the International Bureau of Weights and Measurements to have this standard recognised, and display the correspondence (my application in french, translated via an online english-to-french text converter; any response in english, translated in the same method) alongside the bar. Haven't decided this bit as yet.