Pod Event API

[EdHurtig]

See Also ParadigmHyperloop/hyperloop#43 which will likely define something like this as part of the Telemetry rewrite

In addition to raw telemetry (temps, acceleration, etc) getting streamed back, we also want to support some form of event stream... such as Pod changed software states: Coasting -> Braking would be an event that would be streamed back with an associated timestamp.