My colleague koct9i, whose daily job is developing and fixing OpenVZ kernel, was feeling bored last weekend, and to entertain himself he wrote a small utility called ioping. The idea is simple and straightforward: to wrote a utility similar to ping, which will show I/O latency in the same way ping shows network latency. The idea is very simple but I haven't see something like this. Actually, the tool was written to help investigating OpenVZ bug #1880).
I liked ioping and worked on it a bit, too, just for run. Among some other minor stuff I have added a man page and spec file, so it is now available as an RPM package.
Official project site: http://code.google.com/p/ioping/
My RPM packages and stuff: http://kir.sacred.ru/ioping/