It would be nice to have the option to choose whether we'd like to use a volunteer's general phone number or mobile number for check-in. Currently, mobile number is the only option. (We actually had the mobile number field turned off and opted to use a custom field called Secondary Phone number since many of our volunteers use their cell phone as their primary, not knowing mobile number was the only option at check in.) If mobile number continues to be the only option for check in, I think it would be important to let site managers when they are first starting to set up their site, importing data, and selecting registration questions that mobile number should not be turned off.