Make a font that has the first 4 characters:
[.] [0] [1] [2] [3] [.] [.]
[.] [.] [.] [.] [.]
...
(character chr$(0) is nothing, 1=empty, 3=full)
Then use this to display the battery:
batt% = PLATFORMINFO$("BATTERY")
batt% =MIN(4, MAX(1, (batt+10)/30 + 1 ))
ENDIF
PRINT CHR$(batt%), 300,2
Would this work on all handheld formats (Wiz, iXXX, GP2X etc.)?
yes. I'm not sure if the Wiz battery is properly implemented, though. The rest I am certain about. iPhone had a bug, returning 0...1 instead of 0...100.