You can use a set of inexpensive "Snap" Bore Gauges and a Micrometer or Caliper. You put the guage into the bore and drag it out in a sweeping motion. You can check the bore and the choke separately with a little ingenuity. It's real easy for removable chokes. A caliper can be used to measure the opening (end) of the choke's diameter, but to know the amount of constriction, you really need to measure the bore for a comparison. A longer handle could be fabricated to check the bore diameter from the breech end.
OR, You could spend the big bucks for a dedicated choke and bore gauge in the desired sizes.