Use your phone as a baby monitor instead of buying one UK?

What is the £0 phone-as-monitor setup?

The usual pattern is an old smartphone in the baby’s room (camera + mic, plugged in) and your current phone as the viewer, linked by Wi-Fi and an app. A one-phone version uses the same handset as camera *and* viewer, which only works if a second adult is in the room — it is not a monitor.

£0 is only true if the spare phone still holds a charge, the charger is the original or a known-brand replacement, and nobody else needs that handset.

Who holds the phone — and what happens to the battery?

Which? treats the parent unit as the primary device for watching sleep. Some smart monitors have no parent unit and “you solely have to rely on your phone.” A spare-phone setup is that design taken to the extreme: your daily handset is the only speaker.

• Your phone is busy. A call, maps, or a payment app replaces the nursery feed. The dedicated parent unit keeps talking in a pocket.
• Notifications are not a speaker. iOS and Android can silence banners at night, in Focus modes, or when another app is full-screen. A DECT parent unit is a radio speaker with its own volume and sound lights.
• Two batteries, not one. The spare phone in the cot room needs to stay plugged in. The phone in your hand is the same battery you need at 3am for everything else.
• Which? battery averages (dedicated units): in 2019 tests the average parent unit lasted under 10 hours; audio averaged 13.5 hours and video 7 hours. A phone streaming video all evening is doing the video job on a battery that also runs the rest of your life.

What interrupts a phone that is also the monitor?

A dedicated cheap audio set has one job. A smartphone has many. The practical failures parents hit are mundane:

1. A software update restarts the phone in the night.
2. The app loses the Wi-Fi session when the router hops band or a guest joins.
3. Someone takes “the monitor” to answer a message or pay for parking.
4. The spare phone overheats on charge under a pillow or on a soft surface — a charger issue, not a baby-monitor feature.

If the app is a Wi-Fi camera in all but name, the NCSC smart-camera steps still apply: unique password, updates, and remote access off if you do not need to watch from outside the house.

When does the phone setup still make sense?

1. 1
   You already room-share NHS and Lullaby Trust advice is same-room sleep for at least the first six months, day and night. If the baby is in your room, a monitor is optional. A spare phone is a lot of kit for a nap in the living room you can already hear.
2. 2
   You need a picture for one room, once A weekend in a relative’s house, with a spare phone and their Wi-Fi, can be cheaper than buying a video kit you will not keep. That is a short-term use, not a night-after-night parent unit.
3. 3
   You want your own phone free If the job is “hear a cry while I cook”, a £15–£20 DECT parent unit is the device that does not compete with WhatsApp. Which? audio Best Buys have sat under £30.
4. 4
   You want a picture every night That is a dedicated video parent unit (Which? cheapest video Best Buy around £80) or a smart monitor (cheapest Best Buy smart over £100), not a phone you also use as a phone.

Does a phone setup change official safer-sleep advice?

This page does not grade either setup as safe or unsafe. The Lullaby Trust says there is no research showing monitors prevent SIDS, and that a monitor cannot replace an adult in the room. A phone app does not change that. Official recall checks, if you buy or inherit a dedicated unit, sit on GOV.UK Product Safety Alerts — “not found” is not an all-clear.

In shortIn short: the phone option is free only while you can spare a second handset and you accept that your daily phone is the parent unit. A high-street DECT audio set at about £15–£20 buys a speaker that is not also your alarm, maps and messages. Pick on battery and interruptions. Neither option replaces same-room sleep in the first six months.