When I do web development, I use a custom made logger that catches fatal errors and appends a trace to a file and displays a message to the user. I can occasionally glance
I highly recommend Robbie Hanson's CocoaLumberJack: https://github.com/robbiehanson/CocoaLumberjack
It is very flexible and powerful maybe even a bit excessive if abused. Supports different levels of logging. Logging to files can be turned on with a couple of lines of code and even be sent over the network.