Your friendly picamera author popping up again with an announcement of a project I've been spending some time on recently, which has just reached version 0.3 and might be vaguely useful at this point: Compound Pi.
The purpose of the project is to allow control of multiple Pi camera modules (attached to multiple Pis) from a single client. At the moment the main goal is simultaneous capture from numerous cameras (20+) but in the future I might look into things like staggered capture and so on.
The application consists of a server (daemon) which runs on the Pi (or rather Pis - as many as you can lay your hands on with camera modules), and a client (console and GUI) which runs on Ubuntu (and probably other platforms but I haven't tested any yet). The client controls the servers telling them to configure their resolution, framerate, and what-not, take pictures, and send those pictures to the client. The networking is mostly done with UDP, with broadcasts being utilized for mass control.
The docs (including installation and quickstart instructions) are available at http://compoundpi.readthedocs.org/
and you can also find links from there to the code, bug tracker, and so on. Feedback is welcome, but bear in mind it's a project in its infancy so there's quite a few rough edges (at the moment it's only been tested with 4 Pis, but next week I'm hoping to test it with the full 20+). Also, I've only just released 0.3, so it'll be a few days before the packages hit the Raspbian repos (but the truly eager can find it on PyPI now!).
Author of / contributor to a few pi related things (picamera, Sense HAT emulator, gpio-zero, piwheels, etc.), and currently a software engineer at Canonical responsible for Ubuntu Server and Core on the Raspberry Pi.