LibSysCTr is a utility library that can be used to intercept system call functions on a Linux system. Process monitoring and sandboxing are just two of its potential uses. Internally, it uses ptrace to monitor and report events to the library caller using callbacks. Utility functions are supplied to retrieve information about the process, get/set the system call parameters, and read/write the monitored process address space.
pretrace is a preload library that allows specified (dynamically linked) applications to always be executed under a debugging environment. pretrace allows you to specify the percentage of invocations which will be traced, to help you "keep an eye" on applications without bringing the machine to its knees.