In a BTLE master/slave connection, the master and slave devices synchronize their frequency hopping. Along with the connection parameters (like interval, slave latency, supervision timeout) this allows the master and slave to sleep between connection/transfer events.
With Beacons that advertise (and a phone that scans) it appears that no timing coordination can be accomplished. Basically the beacon advertises at some configurable rate and duration, while the phone listens for an independently configurable duty cycle and duration.
Certainly without establishing a connection the advertiser and scanner can not closely synchronize, but it would seem possible. For an advertiser to broadcast its payload as well as its advertisement settings, and then for the scanner to roughly synchronize its sleep/listen timing to those settings.
Obviously if the phone wants to discover other BTLE devices it would have to scan in the standard manner. But for catching subsequent advertisements of these type of previously heard beacons, the receive window seems like it could be much smaller (even with the wide PPM clock tolerances).
Can this already be achieved some way that I am not aware of? What am I missing?