It is not Bifrost that must support USB OTG, it's the phone! For the DAC, it makes no difference what the source is. BUT! There is a very high probability that Bifrost would only work with UARP/UAPP, as it is a USB Audio Class 2 device, which is not supported even by phones, natively supporting USB audio out, like S3.
Both the phone, and the DAC, both need the right hardware, and the right software, for USB OTG audio to work. If you are saying "The right phones will drive every DAC" I cannot agree. First of all some phones require UARP (such phones have the right hardware, but their manufacturer did not ship an Android software in them with proper drivers). And second some phones, even with UARP, there are all too many DACs they will not drive.
That said I am glad to hear your optimistic assessment of the Bifrost. Though I am still searching for any post that confirms Schiit working with USB OTG.
Edited by Toe Tag - 12/10/13 at 7:52pm