LogWatch and LogSentry aren't mutually exclusive. LogSentry has a separate word filter, which make it a bit more customizable, usefull.
If you're talking Intrusion Detection (IDS) there's only Snort. See here
for my reasons why and here
for an example why.
Some may argue Portsentry v2 is a choice, but it was still beta
last time I checked.
As for integrity checkers there's Aide, Tripwire and Samhain to name just 3. What you use depends on what you're familiar with or need. Like some other ppl
I favour Aide over Tripwire.
Anything else securitywise? Well, search the security forum for the reference list, or ask for it.