For most 'alerts' or notifications the lack of a response may acceptable, and most of the email2sms solutions don't provide receipts, thou using a modem directly you should be able to configure it to request receipts - although that in may only be a receipt that the message was received by the carrier, and not the handset. Some of the receipts we see when sending via SMPP or Telecoms new UAS service (SMPP replacement) are 'number unreachable' (bad number, or blocked off-net number), 'not received' (handset was off for too long so message expired), 'received', 'no funds' (for prepay) amongst others.
Still relies on the txt message getting sent by Vodafone though, and as
there's no ACK on a txt it's not guaranteed, but has been fairly
reliable over the years. The SMS modems seem to die after 3 years, but
apart from that it's been great :^)