I added a service adapter for generating links out to ILLiad. It's only
available in git master, not yet included in a released gem version. Not
yet tested in production by me yet either. (But it DOES have unit tests,
woo).
You are probably using SFX to generate your ILLiad links, if you need
em, and Umlaut just uses those. Which is fine. But if you'd prefer to
wrest control of that away from SFX, an Umlaut adapter is available.
My blog write-up is here:
http://bibwild.wordpress.com/2014/05/07/illiad-target-added-to-umlaut/