For those, such as myself, who were not previously familiar with it:
"MirageOS is a library operating system that constructs unikernels for secure, high-performance network applications across a variety of cloud computing and mobile platforms. Code can be developed on a normal OS such as Linux or MacOS X, and then compiled into a fully-standalone, specialised unikernel that runs under a Xen or KVM hypervisor."
It seems an interesting idea.