Steam has offered a mobile client for a while now. The company now seems to be diverging into non-gaming apps for smartphone platforms.
Steam mobile app for Google Android now feature categories like Accounting, Education and Photo Editing.
These new categories are blank right now. But it is a solid indication that Steam is considering offering more apps through their own mobile app store at least on the Android platform.
Android already has multiple app stores. Amazon offers one of the biggest third party store.