Sure! A stopwatch. If you know the distance from the pitchers release to the catchers mitt, speed can be calculated with some simple math. Lets assume a 43' pitching distance. Add 3 feet for the catcher behind the plate, then subtract 6 feet for pitchers stride, and make it an even 40 feet. If the time from release to mitt is .45 seconds, that means the ball is traveling 40' in .45 sec's or 88.888888' per sec. multiply 88.888888x 60= 5333.3332' per min. and 5333.3332x 60= 319999.99 feet per hour. Since we know there are 5280 feet per mile, we can divide 319999.99 by 5280 and get 60.606058 mph.
If you're her daddy, congratulations that means almost 70!
If you have a Droid or I-Phone there are FREE apps to download that work as a stopwatch and do the calculation for you. One is called "Speed Gun". Just put in the distance - hit start at release and stop at the mit. Mathmatically it's 100% but because of human error it is less than accurate.
You could have her race her pitch against someone driving a vehicle or riding a motorcycle, as they once did with Bob Feller for a publicity stunt. =) Tim Wendel: Bob Feller's Famous Motorcycle Test
I knew a guy who tried to use the pitching machine pitching to one catcher while his kid (and the others he was "timing") throwing to another catcher. If they were the same then he thought the kids were throwing how ever fast the setting on the pitching machine was. His son couldn't throw his way out of a wet paper bag, but based on this test he told people his 9 year old boy was throwing 70.
Simple. Stand 46' in front of the pitcher. Take a pitch on the right thigh. Measure the diameter of the welt. Compare it to a known welt size. I know from my DD that 70 MPH leaves a 8.56" welt.
iF YOU DONT WANT TO INVEST IN A RADAR GUN FIND SOMEONE WHO HAS ONE AND ONCE IN AWHILE GET THE SPeED. TAKE HER TO SHOWCASES. THEY WILL CLOCK HER SPEED THERE AS WELL. THIS INCLUDES MOST CLINICS. IF SHE CAN DUST OUT THE CATCHERS MITT SHE IS THROWING PRETTY HARD.
Tried the timing thingy on the iPhone and my wife is convinced that our 10 y.o. DD is pitching in the high 60s to low 70s. So, I decided to take 8 years off from pitching lessons to give the other kids a chance to catch up. LOL.