How to Store SIP contacts in Google Contacts

If you're having trouble keeping your Google contacts SIP information fields in sync, here a nice tip arriving from a friend.

Seems like the easiest and safest way to add SIP contact information to your google contacts, is to simply add another telephone number field, but adding the prefix "sip:" to it.
That way, it will still be a valid number field, and get synced to all your devices and computers.