On another forum with top shooters they all swear by the Magneto chronograph. However, I don't believe it works on semi-auto pistols currently due to the way it attaches to the barrel.
I've seen that. The report I watched said it worked well on shotguns if adjusted correctly, as it connects directly to the barrel and not resting on a tripod on the ground in front of the barrel.
Shotguns are hard to chronograph as the wad is what seems to be the determining factor, and its quickly stripped when it leaves the gun, so is not a good indicator of speed with a normal chronograph.
If you just want to check your loads a bottom of the line Chrony is all you will need, they are accurate and easy to use. I bought one and am happy with it, no need to invest a lot of money unless you are going to write a reloading book.
I have the Chrony Beta, Master version. The Master has the remote display. The extra memory and shot groups are nice but I wouldn't consider them a necessity. I would however highly recommend the remote display. Having the display right there with you allows you to easily read and operate the device without having to go down range. It's also a much cheaper fix if the chrono ever gets shot. Thankfully I haven't dealt with that yet.