Library PiBeacon

Create beacons in the library to alert patrons of programs and new services when they are in your library. Messages will be sent directly to their phone.

Instructions here: https://learn.adafruit.com/pibeacon-ibeacon-with-a-raspberry-pi/overview

There are some commercial apps available and some libraries are starting to experiment with in-library messaging. Privacy and spam are big concerns. Read more about beacons in the articles below:

Beacons and Libraries
3/2016, Computers in Libraries, Connection, Not Collection: Using iBeacons to Engage Library Users
2015, ACRL, Keeping Up With... Beacons
3/2015, David Lee King, iBeacons and the Library
1/2015, Fast Company, The Internet of Things Plan to Make Libraries and Museums Awesomer
11/2014, Library Journal, "Beacon" Technology Deployed by Two Library App Makers
8/2014, Stephen Abram, Beacons: Emerging Technology with Library Application

More Beacon tutorials:

2/2016, MagPi, Issue 42, p. 38, Sniffur (dog-tracker) [PDF]
9/2015, MakeUseOf, Christian Cawley, Build a DIY iBeacon with a Raspberry Pi
12/2014, TruthLabs, Beacon tracking with Node.js and Raspberry Pi
6/2014, Raspberry Pi Geek, BeaconAir - Track your Pi
5/2014, Wade Wegner, Create an iBeacon Transmitter with the Raspberry Pi
2/2014, PrinceTronics, iBeacon minimal setup w/Raspberry Pi (PiBeacon)