If you JAR file have not JAD , you make with JADMaker.zip :
Download: http://www.geocities.com/mangokun/jadmaker/JADMaker.zip
http://img373.imageshack.us/img373/1...890origvw6.jpg
Open folder :
http://img530.imageshack.us/img530/1...891origdq7.jpg
Drag and drop JAR file to this window
http://img104.imageshack.us/img104/1...892origyi3.jpg
I make test with StopWatch.jar RapidShare: 1-Click Webhosting
Open JAD file with Notepad :
http://img294.imageshack.us/img294/8...900origij8.jpg
http://img295.imageshack.us/img295/5...901origec5.jpg
http://img63.imageshack.us/img63/5658/541902orighi9.jpg
http://img182.imageshack.us/img182/6...904origah5.jpg
Write: SEMC-StandbyApplication: Y
http://img182.imageshack.us/img182/9...906origwc7.jpg
Click Alt + F4 on JAD window and :
http://img259.imageshack.us/img259/2...911origyb1.jpg
Put JAR + JAD in phone and install JAD file , but NO start application , only click More > Wallpaper
OR
Menu > Settings > Display > Wallpaper > Application > and choose application
Here is Clock with edited JAD file to use as Wallpaper -> http://www.geocities.com/bongnate/JAR/Clock.zip