What's your price range? If you have $80 to spend, you can get an embedded module from edpcompany.com like their Sonaswitch Mini-A. It gives you a 10Hz capture rate, and a psuedo-analog output with 10 bits of resolution (0 to 5V). The bad news: product + no product datasheets = 1 major headache. If you have access to the surplus market, you can probably get it for under $20.
Try to search your local component suplyers for ultrasonic range modules.You can also make one yourself from scratch whith ultrasonic trancivers,some op amps and an microcontroller
Its simply timing the echo and then multeplying that whith the speed of sound.
There are schematics for ultrasonic range meters on the net.You can also buy alredy made products that have an laser sight too.
I was looking into these ultrasonic rangers before. Old polaroid cameras used them for the autofocus. do a search for "sun 660" and you should be able to find some info on it. I picked up one from ebay for about 20 bucks...but I guess that isnt possible due to your location, and it required a microcontroller interface.
also, your +5V seems to be sagging a bit...(in your sig)