Liquid lenses have been around for at least the past decade and the theory behind their operation extends back decades before. However, obtaining a lens assembly is rather difficult. Currently, there are several manufacturers that are distributing units: Varioptic's Arctic   , Optotune Tunable Lenses  ,and recently poLight's TLens . Both Varioptic and poLight prefer to distribute to large corporations rather than individual consumers unfortunately. However, Digitus offers a webcam that features Varioptic's Arctic lens and for a very reasonable price. It has been "out-of-stock" for the past several month though and they never responded to my inquiry as to when more would be available. This leaves Optotune's electrically tunable and manual tunable lens but at a vicious several hundred dollars per lens; far outside a likelihood of marketability.
For now, I'll leave you with the future idea of a rapidly focusing lens. The Dynamorph Lens comes from the Ishikawa lab in Tokyo (not for sale...)
EDIT: I've learned Philips also has a liquid lens they debuted in 2004 called FluidFocus  . However, I've found no applications of the technology beyond showing the units at technology fairs. Below is a video demonstrating their lens.