The pest repeller will only work if you throw it hard enough and your aim is perfect.
Don't waste your money.
Your neighbors are breaking the laws, rules and ordinances. Photograph, document dates, times, damage done, cost of plants, etc. Call the Police, Animal Control and the Health Department to report the problem. Your neighbors have the responsibility to either leash their pets or put up an adequate fencing system to contain the animals on their own property. Sure, fencing is expen$ive!! Good fences make good neighbors but good manners are free. Most homeowners have a lawyer they can call; ask your lawyer to write a simple letter telling them to cease and desist. This usually works as most people are afraid of lawyers, mostly cause they can't understand all the whereas and wherefore.