(1) SMS is indeed unreliable; I’ve been using it for paging from a monitoring systems, and they’ve been known to stop delivering SMSes over the weekend. It has improved somewhat of late with the increasing use of SMS, but a couple weeks ago I got alert SMSes 4-6 hours after they were sent.

(2) sftp, despite the name and some of the client behaviors, has no relation to ftp; it’s a completely different protocol sitting trivially on top of ssh. (For amusement, try running sftp-server from the command line sometime.)