Two parents watching one baby unit
One camera, two viewers, and no fighting over who is on duty. Both phones connect to the same nursery unit at the same time, over different links if that is what they have.
How to set it up
There is nothing to enable. Sign the second phone in to the same Slumbi account, tap Parent Unit, and pick the same nursery unit. It joins alongside the first one, and the baby unit shows how many people are currently watching.
The account is the whole permission model: any phone signed in to it can see your units, and no phone outside it can. That is worth thinking about once — a household account is convenient, and it means anybody with those credentials can watch the nursery.
Each phone gets its own link and its own alerts
The two parent phones are independent. One can be on Wi-Fi at home while the other watches over the internet from the office, and each one falls back or climbs on its own without disturbing the other. Alert settings are per phone too, which is the useful part: the parent on duty can have cry alerts as critical alerts that pierce Focus, while the one trying to sleep off a night shift has them off entirely.
Handing over is just closing the app. There is no "release control" step. Whoever is watching, watches; whoever stops, stops. The nursery unit keeps going as long as at least one parent is connected — and it keeps going when nobody is, so a handover with a gap in it does not stop the monitoring.
What the second viewer costs
Nothing at home. Two phones on your own Wi-Fi is as free as one. Watching from outside the house is the paid tier, and it is tied to the account rather than to a particular phone — so a household with Premium can have both parents remote, not just the one who bought it.
Talking, and taking turns
Talk-back is one at a time in practice, for the obvious reason: two voices arriving in a dark nursery at once is not soothing. Whoever holds the button is heard. Lullabies and the night light are shared state — if one parent starts a sound or turns the light on, the other's screen shows it, so nobody is left wondering why the room lit up.
More than two
Nothing in the app limits it to two parents; several devices can watch the same unit. Bear in mind what each viewer costs the nursery phone, though — every additional watcher is another video stream it has to encode and send, which means more battery and more heat on a phone that has to last until morning. Two is comfortable. Five, on an old phone, is asking a lot of it.
If the second phone cannot see the unit
Almost always one of two things. Either it is signed in to a different account — check the email address on both, not just that each is "logged in" — or it is on a different network from the nursery phone and the remote path is not available to it. A guest network counts as a different network for this purpose, even when it is the same router.