The nature of the CVE-2015-0235 makes it impractical to scan remotely. The glibc library is used by many applications which may or may not be exploitable depending on what parts of glibc they use.
Your best bet is to identify which of your systems (they are your systems right?) are using the outdated version of glibc and patch accordingly. Consult with your distribution's maintainer to identify the packages and versions impacted. If you have many systems and don't already have a central patch management system in place, you may be able to write a script to help you identify what versions you're running where.
I don't see any reason that a system behind a load balancer couldn't be vulnerable. Again, it depends on the specific applications used and the setup, but in general, this vulnerability could still be exploited on a system behind a load balancer.