I started using Site24x7 a couple of weeks ago, and this morning I purchased an annual subscription (for about $15). Site24x7 offers easy and fast (and it really is easy and fast) web monitoring services. I'm using them to get alerted when a couple of web apps I'm hosting go down. They send email and text messages. They also provide very nice up-time reports (ad hoc and emailed weekly). I'm sure there are free services/tools out there for this, but this was soooo... easy. I had it up and monitoring in less than three minutes. And the alerts have been timely and effective.

If you have a small buisness montioring need, they might be worth checking out. The price is right, and they offer a wide range of monitoring services. And I just noticed they have a web version for the iPhone. I'm going to have to check it out.