Rumours suggest Google has big changes afoot for its Android operating system, which could involve expanding voice command functionality beyond the search app.

Android Police has word the 'OK Google' feature within the Android Google Search app may become universal across core apps.

The site, which doesn't say where it came by the information, believes users will one day be able share photos in the Gallery app, or reply to Gmail messages by summoning the 'OK Google' commands.

The presence of the functionality would be represented by a red lower case 'g,' the site claims, showing off the feature in a series of images produced base on its information.

The development is still in the early stages and may only appear on Nexus and Google Play Edition devices, the site says.

New Google button too?

Beyond that AndroidPolice believes another big UI change is on the way, with the introduction of a new Navigation Bar.

According to the report, the new ever-preset on screen controls would now feature a 'Google' button, rather than the traditional Home button.

Hitting that would "trigger a search wherever you are" according to the report. How users would get back to their homescreen, if the change was made, was not revealed.

The site has some fantastic, and super-professional looking mock ups of how it believes the feature may end up looking (such as the one we've borrowed). Follow the source link above for a closer look.