While car-detecting devices exist for bikes, including the Garmin Varia, they're largely radar-based. That means they can't distinguish between vehicles of different sizes and only know that something is approaching you, not, for example, how much space it will allow when passing.

Copilot purports to do a lot more:

• Identify cars, bikes, and pedestrians
• Alert riders audibly about cars "Following," "Approaching," and "Overtaking"
• Issue visual warning to drivers who are approaching too close or too fast
• Send visual notifications and a simplified rear road view to an optional paired smartphone
• Record 1080p video and tag "close calls" and "incidents" from your phone