In the clearest sign yet that Apple wants to track our sleep, the iPhone maker has bought a Finnish sleep analysis startup called Beddit, for an undisclosed fee.

The acquisition will help pave the way for Apple to track users' sleeping patterns and combine this with data already collected by the Apple Watch and the company's iPhone fitness app, Health.

Sleep tracking has so far been out of Apple's reach, due to the Watch's battery life not lasting long enough to be worn all day and night for more than 24 hours at a time. The Beddit takeover will address this thanks to the startup's sleep monitoring products.

As well as offering an iPhone and Apple Watch app, Beddit sells a £130 device through the online Apple store, which slips under the mattress and tracks sleep, heart rate, respiration, movement and snoring; it also logs room temperature and humidity, and the data is then transferred to an iPhone via Bluetooth.

Beddit's iPhone app has been updated to reflect the takeover, reports 9to5Mac, stating: "Beddit has been acquired by Apple. Your personal data will be collected, used and disclosed in accordance with the Apple Privacy Policy."

Where Apple goes from here will be interesting. It could create its own Watch app for sleep tracking and include it with the watchoS 4 update expected later this year (and suggest users charge their Watch battery during the day). Or it could develop its own version of Beddit's sleep tracker to provide a more complete solution with dedicated hardware.

Apple is expected to reveal watchOS 4 at its annual Worldwide developer Conference (WWDC), which begins with a keynote address on 5 June. A new sleep-tracking feature could be announced there, or held back until the software is made available to the public later in the year – or even until a third-generation Watch goes on sale, likely in 2018.