Warp Whistle

A Warp Whistle is a magical musical instrument that can be used to remotely activate a warp pad. It resembles a blue recorder and while although it appears someone could use to make music justing blowing into it is enough to activate it.

History
When Greg broke his leg protecting Steven from Lapis Lazuli, Steven let his dad move into the Beach House until his leg was better and his van was repaired. In the same episode, the Crystal Gems and Steven had to go on a mission and before they left Pearl gave Greg the whistle so if there was an emergency while they were gone Greg could alert them and they could return quickly to help. However, Greg quickly began abusing   the whistle and was having Steven rush back home for stupid reasons like to help him find the TV remote. After Steven scolded his dad, Greg confessed that he just wanted to spend time with Steven.

Trivia

 * It's possible that because Greg isn't a Gem he can only activate the warp pad with the whistle.