Hi Dudes 
I have questions about custom probes of the function type.
As I have seen from the examples, there are some functions which can be used:
cpu_usage()
mem_usage()
virtual_mem_usage()
hdd_usage()
My questions are:
Are these functions documented?
Are there any other built-in functions?
I was wandering if it is possible to create probe which measures ping latency: Device would be considered up if the ping latency will be not greater than a specified value.