Its a gimmick, and testament to the proposition that religion is
the bane of logical thinking.
It reminds me of the many quacks in martial arts circles who make
use of suggestible students. Eg. a number of people claim they can
do pressure point knockouts, and by this they mean one-touch (not
one-punch) knockouts. Now, the problem is that they appear only to
be able to do this to their students. This will suggest that the
students are unconsciously faking it. I tink this tongue nonsense
is a variation of that.
Silly christian fundies. 
My view may very well change if it can be shown that the Gibberish
spouted by some is actually a proper Foreign Language that the
utterer has had no experience with. And and i dun mean one or two
foreign words either - i mean proper conherent senteces.
Now, if uttering nonsense if a sign that one has received a baptism
from god, then I, a non believer has received baptism from god
because if i can utter Gibberish. So do all babies. And someone
mentioned dogs too.