Gruber Assist electrifies just about any bicycle and does it in a totally undercover way with most of the components housed in the seat tube and replacement post.
Not quite sure how it all works but there are definitely some rides I wouldn't have minded a little boosteroo up the climbs.
Actually, I wouldn't mind having this set up for every time I hit the climb up to Sand Point in Aptos, that sucker kills me every time and not just because its a big climb at the end up a long, slow climb, its also out in the full sun and steep.
But, being the purist I am, I'd eschew the use of electro-assist and will work on grinding it out myself for that personal accomplishment feeling! That plus, if I had an extra $2500, I'd be putting it towards a new Ibis Mojo.