@adrian78666: maybe I misunderstood your suggestion about GPRS shields, but all such shields I’ve checked require GPIO connections to the main controller. This is unlikely to work with OpenSprinkler, unless if you are willing to have a major overhaul of the firmware. The hotspot device that Samer linked to is much easier to work with as it has a Ethernet port and it’s much more believable to me that you can just plug it in with OpenSprinkler and it would work right away.