You don't really need anything fancy for 'chucks. Any high pitched whistle (including your own, if you can) will make 'em stand up & take notice. They don't call 'em "whistle pigs" for nothin', ya know .
I actually use a "silent" dog whistle. They stand straight up and freeze, providing 4 or 5 seconds for the perfect shot.
As far as actually calling them in, and I may be wrong, but I don't think there's anything that will work for that.