@datanoise: Nickel is monolithic (it's basically a single Qt app, and a main libnickel library). Everything *is* Nickel.
(In practice, it's slightly less cut and dry than that, ePub handling w/ Adobe DRM gets slightly trickier, and some Extras functionality live in separate libraries (i.e., games), but basically, everything ends up running from Nickel the app *and* nickel the binary
).
Which, AFAICT, limits possible interaction with it to monkey patching or preload trickery (c.f., nightmode, whose job is "easy", because it intercepts a public API with public data: an ioctl talking to the mxcfb kernel driver. ioctl is a standard Linux API, and the relevant mxcfb headers are (mostly) public, so we know how to format/decode the data)).