Although folding bicycles have seen somewhat of a renaissance, there has not been as much innovation compared to mountain bikes, because the market is smaller. This is a shame since although there are some great products such as Bromptons or the Birdy, there is, in our opinion, no ideal foldup. An ideal foldup would be one that folds so small and is so light, that you could take it in a backpack, just in case, like carrying an umbrella in case it rains. A couple of the concept designs here come close - vote for your fave.