There are serious security questions here. You seem to think that encrypting the communications is enough. I'm not sure you've done that correctly, as the form you send needs to be completely encrypted with SSL, including all elements (images), or there are potential attack vectors.

As Sean alluded, storing credentials in a cookie, which is an attack vector, is a problem.

However, the bigger problem is you don't seem to think that the fact you're asking people to post security credentials to a form, that goes to your server. You are essentially phishing for people's servers, IPs, user names, and passwords. The user has no verification that you aren't storing this information.

My vote would be no, this isn't useful as a service. As a project I could set up for myself, see the code, and connect to my own servers, perhaps.