The android app that can be extremely helpful when paired with an alarm is Sleep Check Reminder this is an app that has tips and tricks for lucid dreaming. It mostly gives you examples of reality checks to try, but the most useful thing is that you can set a reminder that from your choice of 3- 34 times a day it asks you at random timings if you are dreaming and reminds you to do a reality check. This alarm only uses alarms tones that come with the phone, so if you have an alarm set to your sleep schedule you can set the same sound as the alarm after hearing this alarm all day and asking yourself 'am I dreaming?' hearing your regular alarm will likely induce the same questioning.