Use @'%' instead; '%' is the wildcard character that matches any character any number of times.
EDIT: Note that this assumed you were using MySQL.
Also note that if you want to allow user connections from only two specific hosts (e.g. localhost and a remote host) then you'll simply have to create another user account with identical privileges using the second host name.
The MySQL manual for GRANT explains all of this in more detail and provides examples.
