Most of the ones mentioned above are accurate enough but not scientific. If you want that, go with a Bird43 and you'll need different slugs for different power levels.
The cross needle meters used for Amateur frequencies I'm aware of are selectable peak reading and require 12v to operate the power meter circuit. The CB types like the Dosey and Astatic only require 12v for the meter light so I question their peak reading capability and accuracy.
What do you think of the Daiwa's was thinking Daiwa 501 . Did you say that the 12v input is needed to measure PEP on these meters?
Also, should one pony up the cash and get one with a built in tuner or not?
Cheers