Tongue ID Recognition is batter then face unlock and finger print
Tongue ID Recognition is safe because it is the only organ which is place in our mouth and it is safe too as compare to face unlock and finger print. Every person have different tongue like different shape and surface.There are two major attribute measured for tongue id recognition shape and texture and different people have different tongue shape and texture which keep's safe 
How the tongue differs in all humans it should be not distinguishable
Every tongue has different texture and and shape and i hope it would be use in our smartphone's in next few year's
this is helpful information to human
u can see that technology in your upcoming mobile phones
i agreed whit you Tongue ID is batter then face unlock and finger print