MemoryStick (v 1.3.4, now v 1.4) works well on my iMac G5. And the v1.3.4 also worked on several other iMacs I have tried (G3, G4).
Has worked well in both Panther and Tiger 10.4.2, 10.4.3.
It is a quick and simple way to keep track of the memory and swap file usage. Usually, when number of swap files go up, responsiveness goes down.
FYI, here are the version 1.4 changes, from the help file:
Removed dependence on vm_stat
Added ability to set loudness of sounds
Removed sound options from menu
Added standard Preferences menu item keyboard shortcut"