AFAIK, side arm is the cricket version of dog ball thrower. They have made it sturdy and long lasting, usable with cricket balls. Yes, you can use dog thrower but practice the art first.
I have used the pro side arm version made in UK. Most of the time, loosely fitted balls will land short and v.tight will be beamers. It is all about getting used to facing them. When my friend throws them from right arm over, the ball doesn't comes at an inward angle compared to the actual bowler, it sort of goes straight.
Lots of injuries occur due to side-arm. Even the most accurate of them, Graham Gooch has had mishaps when throwing to I Bell etc. Thrower must and should practice with empty stumps, decide on the way he will throw and the speed.