Is this for iPhones only? Will this work for any Androids?
IIRC its only for phones that came out after the unlocking policy was changed (2/18/15), unless its an iPhone 5s and up.
ETA: "Generally, if you have a device that was launched prior to February 2015 and it is capable of being unlocked, Sprint will provide a bill notification and/or text message when you are eligible to have your device unlocked. The bill notification will direct you to Sprint Customer Care who can assist in efforts to unlock your device.
For domestic SIM unlockable ("DSU") devices launched after February 2015, Sprint will automatically unlock the device when it becomes eligible."
Then there's a chart showing only iPhones as DSU unlock-able, so it doesn't sound like Android has changed much, unless its for international use.
Also, keep in mind that many Android phones aren't the correct chipset to be used on other carriers, so even unlocking them might not do anything useful for you.