Michau's Battery Meter is probably the only PalmOS utility that tells you how long your battery will last until you need to recharge it. Need to use your PDA for a long time without a charger? Check if your batteries won't dry out before you finish your work!
Another feature is the battery icon in menu bar. Now you will be able to know your battery status in all applications, any time! Just see below how it works:
Open your menu bar, and you will see an icon indicating your battery level. You can do this in any application - no need to switch to application launcher in order to see the battery status! Also, on some handhelds (like Zire 21) the launcher does not show the battery level when charging - here you can see it too!
Alternatively, under PalmOS 5 you can use live battery measurement. This option will measure your battery usage as you go, adopting in real-time to your current battery usage. You don't need to calibrate the battery when using this option, but you need to use your PDA for some time until enough measurements are gathered.