Best protocol for low duty-cycle, low latency application (e.g. keyboard)

[Superposition1]

Our application is similar to a wireless keyboard. The events are very sparse but we need low latency (~50ms). If I understood correctly, BLE is a synchronous protocol, meaning that the connection interval must be equal to or smaller than the required latency. For example, if we want a latency of 50ms then we need to send messages at 20hz continuously. But that's very bad in terms of battery life. What protocol should we use?

[run_ar]

I would use BLE with slave latency. i.e. if you have a slave latency of 4, the keyboard would not have to wake up and listen to those (4) events from the master unless there was an ongoing timing related link layer process.