Dear Krishna, I embed a link to one of Larry Ferlazzo's blog posts, as well as a link to a general search about his work. He does excellent work in this field. Good luck!
I commending for exploring mobile learning for your ESL students as today's digital natives have preference for flexibility in learning anywhere and anytime via their mobile devices. Here's some recent research I did on flexible learning environments and what's available in RG that I hope would be helpful for you. I extend best wishes for every success with your research in the New Year!
Actually, there is growing research that shows that the idea that "students can learn at any place or time" has pitfalls.
I have seen research that shows students prefer to set aside time for studying, regardless of whether it is on their smart phone or otherwise. Many resent forcing them to use their personal devices for school at times they prefer to be using them for themselves.
In addition, online lessons that are intended for "any time and any place" must avoid critical thinking and time consuming steps, because "any place and any time" may only consist of a minute or two at a time.
But fundamentally, training students to listen means providing them audio or video which they need to understand and find meaning. You need to consider whether this is best done via smart phones or some other instructional technique.
As indicated in the attached document, you should FIRST determine your class outcome requirements and then the kinds of learning activities that will allow students to achieve those outcomes. FINALLY, consider which of those learning activities can be performed via technology.