Update: Works on iOS too.
Try:
function checkIfFileExists(path){
// path is the full absolute path to the file.
window.resolveLocalFileSystemURL(path, fileExists, fileDoesNotExist);
}
function fileExists(fileEntry){
alert(«File « + fileEntry.fullPath + » exists!»);
}
function fileDoesNotExist(){
alert(«file does not exist»);
}
Found the solution here.
Works on Android. Will test on iOS and update this answer.