I was looking for Android Dual-SIM API for Android, but more or less I found nothing. As far as I understand, there is no public API from Google/Android, only specific implementation of each manufacturer. Therefore is very hard to implement application supporting Dual-SIM (or more SIM) devices.
If I am not wrong about it in this time (17.02.2015), is there anything we (developers) can do to request/force Google to implement this?
I would like to "guide" all developers to same place (if there is one) to increase our power.
Thank you for any feedback.
[UPDATE: 10.03.2015]
Android support DUAL-SIM/MULTIPLE SIM cards in API since ANDROID 5.1.
Whether you want to share your phone with a family member or better manage your mobile costs, Android Lollipop 5.1 now lets you use more than one SIM card on a device with multiple SIM slots.
Read more here and here.
Answer
AFAIK, Google has never openly discussed their rationale for not supporting multi-SIM devices out-of-the-box, even though manufacturers are quite clearly gung-ho about it. None of Google's Nexus devices has had this feature, so obviously they do not advocate multi-SIM devices, whatever their reason.
I suspect it has something to do with security, and also with Google's perception of a smartphone being an abstraction of an individual, and all data being connected with a single phone SIM account, and thus representing that individual. Or maybe I'm crazy.
The official Google review branch for this feature is here. And the only relevant post on SO for working around this is here.
UPDATE:
Both Multiple SIM Card Support and True multi-user support are available.