Control, accounts and offline use

A device controlled by an app is hardware plus a service. The hardware is yours. The service can change after the sale: features can move behind an account, a server can be retired, or an app can stop being updated for new phones.

So the useful question is what the device does when the app is not there.

Whether it does anything with no phone and no internet. Some devices have physical controls that work on their own, some have a single button that only pairs, and some need the app for everything.

Whether the app needs an account for the first pairing. If it does, the device cannot be used out of the box without one.

Whether control passes through a company's servers or stays between your phone and the device. Local Bluetooth control keeps working if a service ends. Control through a server does not.

Every app on a major store declares what it collects, what it shares and whether you can ask for that data to be deleted. Those declarations are public, sit beside the install count and take a minute to read.

They are the developer's own statements and the store does not verify them, but they are still the most specific information available about a device you have not bought.

A device whose firmware can only be updated through its app depends on that app for fixes. When the app stops working on a current phone, the device stops receiving updates.

Look for physical controls that do the whole job, with an app as an optional extra. Ask whether the device powers on and runs a pattern with no phone present, and treat a device that needs an account to work the first time as one that always needs an account.

Choosing app-free is a reasonable preference. It is the version of the product most likely to keep working for years.