First of all, jaywalking shouldn't be illegal but these laws are ridiculous.  There is nothing wrong with texting while crossing the street, I don't recommend it and don't do it my self but this does nothing to stop the actual problem, people driving their cars into pedestrians.  

Now, if you're going against the signal or crossing in the middle of the street while on your phone and are clearly distracted by it, resulting in a crash then I think there should be some leeway to hold you at fault.