We had a lot of fun with the DS1, a stable and compact range sensor, based on TOF, but it's limited to distances of around 2m. We were wanting a longer range sensor, and unfortunately the ultrasonic sensors didn't have the 7m effect we were looking for (they performed closer to around 3m, which is a shame.)
Now based on josiahnelson's idea, we'd like to keep looking for a longer range TOF. We found a robotics TOF sensor, the STP-23L, which has a nominal range of 7m, but of course we thought it would be nice to get 6m.
There is also a model of the STP-23 without the L, which can reach 13m, which is crazy, but it comes with increased power consumption.
So ideally we might have a chance to build a tof sensor over 5m with the STP-23L.
Due to the distance, we made a special enquiry to make sure that the sensor is FDA Class 1 laser safe and safe for pets and human eyes.