My wife bought a roadster (made by Motorola) and really liked it so she let me try it. She bought it mainly to play her music and answer calls. She has an iphone and it worked well. I have an "X" so when I started getting it paired and ready to use I found out about MotoSpeak. So I downloaded the app and used it. It was at this time, I ordered a Roadster for myself through Amazon. I thought it was really cool the way it would read text messages to me and then allow me to reply using voice to text. At this time it wouldn't allow the initiation of a text using voice to text. I also liked the feature that allowed running the voice throught my cars radio speakers... both calls/texts and when using my GPS.
Anyway, sometime later MotoSpeak was updated to allow the initiation of text messages using voice to text. I find if speak normally (perhaps slightly slower and enunciate my words) it is pretty accurate. It's not perfect but if I just redo the message being a little more careful when speaking the problem words, it gets the message correct. Oh yes, It also allows voice dialing through my phone contact list.
So, to answer your question, I have never tried drivesafe.ly but I use Motospeak almost everytime I drive, and really like it.