Critical Maps is a free iPhone app designed for participants of the Critical Mass movement. Developed by Norman Sander, this app allows users to share their GPS coordinates with other participants, making it easier to navigate and stay connected during the event.

The main feature of Critical Maps is its ability to share GPS coordinates. This feature enables users to see the location of other participants in real-time, helping them stay together and navigate through the mass ride. It also enhances safety by allowing users to keep track of their friends and fellow riders.

In addition to the GPS sharing feature, Critical Maps also includes a built-in chat function. This allows users to send messages to each other within the app, making it convenient for coordinating meetups, sharing information, or simply staying connected during the event.

It's worth noting that continued use of GPS running in the background can significantly decrease battery life. Therefore, users should be mindful of their device's battery usage when using Critical Maps for an extended period of time.

Overall, Critical Maps is a valuable tool for participants of the Critical Mass movement. With its GPS sharing and chat features, it enhances the experience of riding in a mass event, providing a means of communication and coordination among participants.