Yuh, I stumbled on this a couple days ago. Needs some tweaks, good suggestions in the comments, but a brilliant start. They've since taken it on a mountain trail and shaken out some other to-do items.
Take-away phrase was (paraphrasing from memory) "Until now, my mobility was limited to the pavement." Look on her face as she tried a curb, rolled over a grassy parkway, etc., is priceless.