updated 02:06 pm EDT, Wed June 4, 2014
May improve odds with lost and stolen devices
The iOS 8 incarnation of Find My iPhone includes a new "Send Last Location" option, notes AppleInsider. A description explains that toggling it on will send the last location of a device to Apple once the battery drains "to a critical level." It's not known how this information will be shared with device owners, or how long it will persist.
Find My iPhone currently holds a device's last-recorded location for 24 hours. By allowing iOS to force an update immediately before a device powers off, Apple is presumably hoping to maximize that time. It may help in retrieving a lost or stolen product, although in the latter case it may be possible to restore iOS and break Activation Lock before Apple can get an accurate location.