Pin unlock without showing numbers
Since I just upgrade to 5.0/Lollipop, I can't confirm for sure if this setting is present in KitKat/4.4, but in 5.0, you can hide the last digit in the PIN unlock screen by turning off the Security setting labeled Make passwords visible, as seen here:



This is found under the general Settings app under the Security section.  Note, however, that this also affects password fields elsewhere in Android, such as in the Chrome browser.