Yes it will be possible to have a user with a feature phone to auto check-in but that will be from an application level. My company http://www.saya.im has a chat application tailored to feature phone and one of the features is a geo-location chatroom. We are able to do this using cell-tower id's and triangulations and augment that with the phones IP address. There are open-source cell-tower id databases like http://www.opencellid.org/ which can be of help. Also you may want to think of a Java ME app to implement this.