I started whispering to them instead of raising my voice, which worked wonders. That's when I got into all the positive discipline and non violent communication principles, which I found could be applied to infants as well as teenagers, and even young adults.
The first app I found, Positive Discipline Parenting Tool Cards, contains a collection of 52 cards based on principles shown in the "Positive Discipline" book by Jane Nelsen, reminding you of what you can do to calmly but firmly assert yourself and connect with your children.
Another one I thought worth mentioning, Tantrums 911, is by family therapist Valery Jamposky, who has based her method partly on Marshall Rosenberg's Non Violent Communication techniques. There are suggestions, including videos, for steps on how to deal with different difficult situations without necessarily raising your voice.
Do you like a particular app to help with discipline in a positive way?