Hi, I'm Th o, a trail runner from France and the maker of Mapulse.

Last July, three of us ran the same trail race on three distances (90, 40 and 28 km). Each of us sent our position to our own people by text, WhatsApp or Find My. Not everyone had WhatsApp or an iPhone, and the friend driving between aid stations for all three of us never saw everyone at once.

Mapulse came out of that day. Two things mattered most to me:

• several runners on one map, behind one link;

• the mountains: when the signal drops, the phone keeps the data and sends it when the network comes back, and the page says the position dates from before the dead zone instead of pretending it's live.