The NTi XL-2 is one of the most awesome tool we have at work! I'd buy a kit myself if I was touring or full time freelance engineer. Don't need to own it as an in house technician.
Has an RTA, oscilloscope and you can display all sorts of metering at once (I usually have it showing Aeq5", Aeq10', Apk, Aslow and Cslow all at once). We have a kit that includes the MR-Pro so it's a great kit.. Rather expensive but you get what you pay for !
It does auto off when running on batteries, haven't checked if I can turn that off but it stays on when plugged in.
It can also be connected to a computer and used as "sound level predictor" for when working on a db limit.