Network Monitoring Tools

[Ki Song]

Our company is having some issues with a web hosting provider. The server we
have with them (at a remote location) crashes ... sometimes more than once a
week. 

We are an e-commerce company, so whenever our site is down, we are losing
orders!

Is there a network monitoring tool that I can install on a machine within
our own network that will monitor the server uptime of our server that is at
a remote location?

I want a tool that will monitor the server, make sure certain services are
working, and then, if they are not, to either text message me, or e-mail me.