Crying need is an informal expression for a desperate or a very strong need for something (or someone). For example:
There’s a crying need for skilled craftsmen in most developed countries, as most people are not willing to work manually anymore.
It can well be used sarcastically; the following example is taken from Sherlock: The Empty Hearse:
Sherlock: I’ve written a blog on the varying tensile strengths of different natural fibres.
Mrs. Hudson (with a teapot in her hand): I’m sure there’s a crying need for that.