It's fitting that this invention comes from France, a country with a lot of outdoor cafes and a lot of cobblestones. Fixmotion's outdoor tables feature a self-stabilizing leg design:

Best of all, you don't have to futz with anything. You just put the table down and it does the rest. "Our tables will always be stable even on your paved terraces without any action on your part, no adjustment, no locking," the company writes. "Goodbye to tedious and temporary wedging."

The legs can compensate for a 5cm (2") vertical difference on the diagonal.

There are four different designs, and the tabletops all fold vertically for storage.

It should be noted that the design is self-stabilizing, not self-leveling. The latter would require significantly more complexity; perhaps a company in Germany will tackle that one.