Set the windward mark for a session and the app unlocks mark-relative tactics: VMC and DTM in race views, laylines on the map and in Replay, per-beat Coach findings, and auto-scored Mark Roundings in Training (sail within about 30 m of the mark and back out, and the rep is detected and coached; without a mark the drill is a manual +1 counter). With no mark set, nothing changes.
Neither device captures the mark live. Pinging it means sailing over it and tapping at the moment of a rounding, the point in a race when a hand is least free. Place it on the map afterwards instead: open the session, tap the flag in the track map's control bar, tap the water where the mark was (your beat's turning point makes it easy to spot), tap again to fine-tune, then Done. It's saved as an estimated mark, labelled "(est)", so treat its layline calls as good to within where you tapped. The trash button deletes it; the undo arrow puts the course back the way you found it.
Offset marks, gates, and full course templates are planned.