You're looking for a "smart baby monitor".
However, asking to have a baby monitor that comes with both a proprietary viewing device and and mobile app is probably asking too much from the manufacturers.
Developing hardware to view the baby monitors requires the manufacturer to have:
- More materials costs
- Increased engineering costs for developing the hardware
- Software development costs for developing the software
- More limiting computing constraints based on need for minimum-spec hardware
Developing an application for smartphones is seen as an alternative to physical devices. You're already providing/own the hardware (why may be better than the hardware they produced), so they can put their resources into the software development aspect of the viewing app.
Since apps are an alternative to, rather than a supplement for, proprietary hardware I'd be impressed if any such products exist.
Even if such a product existed, the dedicated viewing device would most likely have less features and feel terribly basic when compared to the app.
However, you can get your solution yourself just by looking for a smart baby monitor.
Searching Amazon, for instance, with those terms brings up at least 4 monitors with Android/iOS apps in the first 10 hits.
Brands listed include:
- WiFi Baby
Of the models I quickly found, they have a wide variety of features, so make sure you're looking for other features than just being Android/iOS. Some features are:
- Pan and tilt
- 360 rotation
- Night vision
- 2-way audio
- Video recording
- Multiple users (AKA, more than 1 smart device can be used to view the monitor)
- App support (how old is the app? Is it being updated regularly?)
Minimum requirements for the app
Some smart baby monitors don't come with apps, but have proprietary handheld video monitors and web-based features that make them "smart", so be aware that calling it a smart monitor can mean different things. However, this should at least guide you to finding a device.
To get your 2nd device that you can leave downstairs, you can simply purchase or acquire another smart device. You can buy a pre-paid carrier phone and not use it as a phone at all, and use only the baby monitor app. There's a wide variety of low-cost tablets available these days. You may also already have old smart phones you haven't recycled that can be used.
While this may seem like an additional expense, I would argue that it's probably not any more expensive than a product that would have both a dedicated viewer and a mobile app.
Economically speaking, it's in no one's best interest for a manufacturer to provide both.