Teardown: DDC Mobile X900
Nick Poole 
Bag of Chips
I guess we've seen the dirty truth, but we can't know the whole story until we get a handful of datasheets. Let's start looking for part numbers:
Found one! The silkscreen on this camera module turned up the datasheet for an image sensor called the GC6123. An image sensor that must be in demand these days with its whopping 240x320 pixel resolution. That's a small fraction of a megapixel!
Ah ha! The brains of the operation! Both of the ICs pictured above are made by the same company: RDA microelectronics. This is the first time I've ever had trouble searching for a datasheet because the part number brought back more forums than anything. Forums full of people trying to get tools and firmware to reprogram the chips in order to make cheap phones and clone IMEIs. Apparently, the RDA8851C is a very popular controller in these inexpensive Chinese cellphones. And why wouldn't it be? Integrated flash on chip, camera interface, keypad scanner, quad-band integrated transceiver... in a way, this thing is the phone.
The only component that doesn't seem to be integrated? The front-end RF module. That's where the RDA6625 steps in.
Okay, we kind of get how the phone works now but let's revisit the battery. Truth be told, that 18650 wasn't the only thing in the battery enclosure. I also found this:
A board containing a pair of battery protection ICs:
The S8205, which protects multiple cells from overcharge, over-discharge and over-current.
And the DW01 which seems to do exactly the same thing only for a single cell... which this is. This leads me to believe that the battery board is used in multiple batteries, you'd probably find the same board in 40% of li-po batteries in China.