The app has a number of features. Once you click on it it goes into driver mode. This can be toggled off if required. By default the app handles texts and speaks the text message to you. Calls can be handled as well. In both cases the person calling and/or texting get an automated reply to say you are driving and you will call them back. In the case of a text the first 100 characters are spoken to you and it says who the text was from. This means you can ignore the phone whilst driving because you know the person calling/texting is aware of what you are doing and you can hear a snippet of the text. This adds to driver safety because the driver would be less inclined to reach for the phone, which is dangerous and illegal. The app provides a list of who called/texted and how many the app managed. To get speech working you will need to switch on Text to Speech (TTS) on your phone. This can be found under language and input and then text to speech options. If you have another text client which overrides the standard android sms, you may need to reduce its priority to allow the app to see the message. Some 3rd party apps grab the text process it and then remove it. You will find options, hopefully, in such apps where you can reduce its priority or get it to pass the text along the line.
