It seems something for men already exists... and it's damn near 100% effective (1 out of a 250 member sample had an unplanned pregnancy), non-hormonal, completely reversible and a single procedure works for 10 years. If you want it undone, the procedure is equally simple and reverses itself in 3 months.
http://techcitement.com/culture/the-.../#.UPES04njm2t