>real Ben Torah with a smartphone
> what do you think he does with it?
I would first need to know who is BT? (dubious acronym, that I need to clarify with even more dubious: Ben Torah, NOT Baal Teshuva, to which Gerer Rebbe would answer – “why NOT”). I see multiple references to BT – from R Feinstein to R Lamm, but I do not see a clear definition. I am guessing this is a slightly lower level than Talmid Chacham: TC someone who strives to be a full Chacham, but is humble to call himself the one – and BT is someone who seems to claim that his behavior is fully guided by Torah, but not ambitious to become a Chacham? Sort of a Talmid who is on non-degree path?
So, if we were to talk about TC, halakha is clear: you presume the best. So, I would think that his wife is expecting or/and his mother is not feeling well, so he needs a call. Or he is a doctor or a real estate broker and the phone is part of his parnosa, or he is learning off YUTorah site (or is this l’gnai?). Of course, none of this releases him from other halochos – greeting people first, not bumping into them while walking or driving.
So, if BT is a lower level than TC, I am not sure whether we have to give hum same benefit of doubt. Possibly, we give it to TC because he is constantly reviewing his behavior (do not question him in the morning about aveira he did yesterday night, as he surely did teshuva). If BT is not doing that, then he may not deserve the benefit, and if he does – then he is TC!