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.
psinfo shows process information and statistics using the kernel /proc interface. This information includes: process state, environment, arguments and flags; CPU usage; scheduling; I/O usage; virtual memory status; pagefaults; capabilities; and signals. psinfo is useful for providing a detailed view of the current state of an application when diagnosing issues or performance problems.
pwatch is a set of tools for analyzing what a process is doing. Only the "io" command is currently implemented. It presents I/O activity in a nice ncurses screen and allows you to sort by the read/write speed or the number of bytes read/written since the start of the program. It was written to easily detect which program is eating a lot of I/O bandwidth.
scanmem is a simple interactive debugging utility for Linux that can be used to locate the address of a variable in an executing program. scanmem can then be used to modify the variable once, or continually over a period of time. It is similar to the "pokefinders" used to cheat at video games.