Server Monitoring Software

Would like a small piece of "client" software created that can be installed on a Windows computer, and will routinely connect, via the Internet, to a piece of created "server" software.

The "client" should run ideally as a service in the background, with minimal resources used on the Windows computer. Over time I may request addition changes - such as the client sending info based on disk space, event logs etc, but initially I'd just want it to connect to say "hi" and tell the "server" it is online and working.

The "server" should be able to display all registered "clients", those that are currently online, those that are offline - and for how long etc. I may then request additional alerting in the future - such as sending an e-mail if a client is offline.

I'd like the client to be compatible with Windows XP, Vista, 7, Server 2003 and Server 2008. The server just needs to be able to run on anything, such as Windows 7.

I am aware that there is software out there at the moment that does this, but I'd like to look into the possibility of having my own built, which can then be customised in the future. So unless you know something that is easily customised etc, no need for referrals please.

There is no urgency on this job, and I will only likely proceed in the short term if a very good bid comes in, else I'll keep looking. Budget here is flexible if the right proposal comes in, as I am not sure what sort of cost this would involve.

Thanks