In case there's any ambiguity, Cloudkick isn't giving a cloud server instance to everyone for free. The developer plan lets you monitor and manage one server for free. It has all the other features of paid accounts though: SMS alerts, custom plugins for monitoring, etc. I use it for my one EC2 instance that acts as my personal web server/IRC bouncer/VPN server/whatever.
I tried to add a cell number for getting SMS alerts. The "save and test notification" prompted me with "Notification sent!", but several minutes later I've yet to see a message.
In case there's any ambiguity, Cloudkick isn't giving a cloud server instance to everyone for free. The developer plan lets you monitor and manage one server for free. It has all the other features of paid accounts though: SMS alerts, custom plugins for monitoring, etc. I use it for my one EC2 instance that acts as my personal web server/IRC bouncer/VPN server/whatever.