To access a web service (or any web content) from your mobile phone, you need the machine where this content is located to have a Public IP (and this to be publicly accessible).
Depending on the provider you use for your network connectivity, you could have one.
A simple way to check this out is this:
* retrieve your public IP (i.e. going to
www.whatismyip.org)
* start your webservice
* try to access your web service via your public IP
Note that, if you're behind a router, you should first configure its NAT settings to let your local IP be visible from outside on a particular port.
Another, simpler, way would be to check for (free?) hostings that allow you to publish your content on their space.
Hope this helps!
Pit