You all may have heard by now that all humans use echolocation to some degree, and some of them, out of need, have managed to master the technique to remarkable heights. Fact is, some boost to our body equipment is needed to reach the level of precision of dolphins, bats and other animals. Research by academics has consistently shown that training is quite easier than expected, with sighted subjects starting to notice obstacles within hours, and to differentiate objects in about a week.
The solution would probably be either a cochlear implant or one straight to the V1, plus a sonar conveniently standing on a headset for signaling. Daniel Kish and co. have been working on such a device for several years (no news made public on the results so far, though), Warwick did some incursions into it, and now Cannon and Saver are tinkering with their magnet implants to develop their own "bottlenose" haptic echolocation-like system. There are commercial sonars for blind in the market, many handheld, most also haptic, and all of them failing to deliver significant results.
We are simply talking about automatically emitting a signature sound in the right set of frequencies and intervals by a sonar, and getting feedback from the surrounding at a much, much higher resolution than natural echolocators can manage to do (see Underwood, Bushway, Kish and others), straight to the inner ear or ideally implanted in the "visual cortex". The brain would do the rest, specially in those than lack visual input and therefore can use the processing power left unused to navigate using the new data flow. If people manage to get results by clicking their tongues, imagine what could they do with proper gadgets.
This would potentially mean being able to see in the dark, "structures such as bones, and even certain objects inside a bag", and more, as Professor Juan Antonio Martinez of Madrid's Alcala de Henares University reported in '09 , "this would be a new way of perceiving the world". As far as I see this is an area with huge potential, both for the blind and sighted people. Anyone willing to work together to make it happen please get in touch.