Whilst I like the sentiment, and when I have parties at my house I try to encourage the whole "leave your phone by the door" thing, I don't really like this.
When I'm in a pub, I'm generally not on my phone, and I'm quite conscious of trying not to use it unless I'm sat waiting for someone or similar. However, I always have a phone with me in case of emergencies (which means being reached, not just making calls out), and I'd hate the idea of that being blocked.
Not just that, but I'm often on-call (with either a phone or pager) but will still go out and socialise, in this situation this establishment is one that has to be avoided.
Good idea/sentiment, bad execution.