The Audemars Piguet caliber 2923 is a hand-wound chronograph pairing the rattrapante & flyback functions in previously unseen fashion, making it a 'Laptimer' according to the manufacturer. It is said to be developed at the request of Michael Schumacher, who asked the Audemars Piguet technicians wether it'd be possible to make a mechanical watch capable of measuring and recording an extended series of consecutive lap times.
Caliber 2923 features two superimposed central seconds hands, just like a normal split-seconds movement. The There are three buttons: one for start/stop, one for reset, but the magic is in the third push piece: it stops one of the two seconds hands, while simultaneously restarting the other - thus allowing its wearer to note down one lap time, while the timing for the next lap has already started.
The regular reset button can also be used to 'flyback' the one seconds hand that is running at all times, without the need to stop it first; a function useful when, for instance, the first time must be kept as a 'reference' time for the following laps.