Saw this company at a design conference a couple of years ago and thought they looked pretty cool......quite tempted to get one to use for commuting in the summer......
And the honest truth of it is. People, when together or more than one, will slate it, if an adult went past on one of those, what was or started off as a kids toy or mode of transport. Nothing wrong with the idea being a sound one
Any of those who slate it in a group will when along ,and if trudging it home, think 'Now thats not a bad idea' or the thought of 'that blokes going to get home long before me'.
This one looks quite easy. There is many other versions/designs ontinterweb this was just the first I found.
Could make one out of a crappy mtb front end with 26" wheels up front and smaller at rear.
You could build it as you like.