My son just activated his Motorola Razr M phone, and we can't get Family Locator to give "improved accuracy" locations. Google Play does not pull up the VZ Family Locator app in Google Play from the Razr M. I spoke with Verizon tech support level 2 for about an hour today, and they were unable to find the Razr M on a list of compatible/capable phones.
On a related note, the Family Locator page http://www.verizonwireless.com/familylocator does not have a link to a list of compatible phones!