I think this is useful questioning. My response is to ask, when one is on the cell phone at the beach, can one be mindful of both places at the same time. My concern with various forms of meditation is that they have equal possibilities of withdrawing from other people, from connectedness in that sense.

“With our mobile phones and wireless palm devices, we are now able to be so connected that we can be in touch with anyone and everyone at any time, and do business anywhere. But have you noticed that, in the process, we run the risk of never being in touch with ourselves?”

http://www.resurgence.org/2007/Zinn241.htm