I was googling for info on something called "squishy baff" that my kids want.
I found your query that way, and also found this (sorry about the ugly link)
http://www.google.com/url?sa=t&rct=j&q=sodium%20polyacrylate%20gel%20as%20soil%20amendment&source=web&cd=1&ved=0CEwQFjAA&url=http%3A%2F%2Fwww.eurojournals.com%2Fejsr_25_4_04.pdf&ei=4AjFT6ylN8bW2AXg9qho&usg=AFQjCNEEeSWakJ56jUZUPv3GyKe7GwkB2w&cad=rja
It's a journal article "Polyacrylamide Polymer and Salinity Effects on Water Requirement of Conocarpus lancifolius and Selected Properties of Sandy Loam Soil" that gives a lot of breakdown about the chemical properties of polyacrylamide gels in soil and how they affect plant growth.
I would not use it near structures due to it's expansion potential. Clay is bad enough, this stuff sounds like it could screw up a slab foundation pretty thoroughly ;->
From what I'm reading here, I don't think I'd personally worry about using it on food crops. There's weirder/worse stuff already in the soil.
The urine is a factor only in that it can attract/nurture bacteria that you might not want around your food plants, and I know that some infant/toddler immunzations carry a warning about safe handling of wastes for a period of time following the immunizations, so if that's a factor, you'd want to read up on it more.
But I don't think I'd have a problem using it for ornamentals and bug-gardens (although in theory the bacteria could harm the bugs, but they seem to do ok around my cat's "Facilities", so I probably wouldn't worry about it in practice.
(And I might let my kids play with it, once saturated, but probably not bathe in it ;-> )