Porchlight, with an alarm on the promise

Field notes

The service uses a deadline rather than continuous location sharing: the user writes a destination sentence, sets a time, and may add a vehicle plate before leaving. If the check-in does not arrive, chosen contacts are alerted, reminded four minutes later, and escalated; the page says watches last no more than 18 hours and preserve their records as read-only. The browser version is described as available now, while native iPhone and Android builds are listed as forthcoming.