The GXV models are said to be based on Texas Instruments 6000-series DSP processors; most of these are built from an ARM processor and a DSP core. There are no details to me known about these phones. You are welcome to send me one (or two, so video can be tested) if you want to see them analysed ;-)
There is a toolchain for these processors for free download from ti.com, but a recent contribution of gcc support for tic6x is expected to be included in an upcoming release.
The GXV3615 and wireless GXV3615W are "cubic" cameras, equiped with a speaker and microphone. Their standard firmware can mail, dial, and FTP security incidents (detected motion). No support for IPv6 or ZRTP, though...
This device might make for a very advanced doorbell, once 0cpm Firmerware is installed on it :-D -- but it would take a bit of thought to avoid an alarm with every post officer dropping off a letter.
According to its user manual, the embedded video chip is an Aptina MT9V136 -- which has an NDA-protected datasheet. NDA's and open source don't mix very naturally. But earlier chips in the series, like MT9V112 and MT9V135, are available without NDA, probably because they are not the hottest anymore. The table below lists the available flyers and datasheets for comparison and extrapolation.
Flyer Datasheet MT9V112 flyer MT9V112 datasheet MT9V135 flyer MT9V135 datasheet MT9V136 flyer Under NDA on Nov 24, 2011