Well said. Some people like me would never bother to stick on the exercises until a companion pushed us so. But as you said, such apps can be our good companion and keep us motivated.
In my samsung android phone, there is built in app 'Samsung Health'. This app counts the daily foot steps I walk and notifies me from time to time to take few more steps to achieve target. Sometimes it encourage us by giving awards on completion or exceeding target. Now I have found pleasure and companion in form of mobile app.