Сделайте что-то вроде этого:
int showLimit = 20;
/* Get all Tasks available (with limit set). */
ActivityManager mgr = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE);
List<ActivityManager.RunningTaskInfo> allTasks = mgr.getRunningTasks(showLimit);
/* Loop through all tasks returned. */
for (ActivityManager.RunningTaskInfo aTask : allTasks)
{
Log.i("MyApp", "Task: " + aTask.baseActivity.getClassName());
if (aTask.baseActivity.getClassName().equals("com.android.email.activity.MessageList"))
running=true;
}