Using webservices to connect two different computers throught the midway webservice.

Hello experts,

I plan to make a tool to connect my home computer to my laptop and android phone that I carry around. The connection would basically include some features like showing up status of download progresses, capturing images using the webcam, etc.

I was asked to use port forwarding but that is not an option, as my home computer uses a cable internet connection that does not give access to the public ip, and the phone and the laptop both use my phone internet connection which does not provide me a public ip either. So, while looking for solutions, I came to know, setting up web services might be of help.

Now, what I want to know is that, is it possible to set up a web service on cloud such that I can ping the web service from my phone with specific commands when I want, and my home computer on the other hand keeps looking for requests at the web service every minute and as soon as it finds a ping from my phone, it executes the command requested and forwards it to the service, which forwards the result to my phone?

In case that is possible, can free webhosting sites be used to host such services??

P.S.- I plan to write a simple SOAP service using PHP if this can be done, and I would need some help in setting that up too.

Help is much awaited.

Thanks in advance.