msr
A ruby gem for controlling magnetic stripe reader-writers (on UNIX/UNIX-likes).
Uses libmsr.
Roadmap
require 'msr'
msr = MSR::MSR505C.new("/dev/ttyS0") # or your serial device
puts "OK" if msr.linked?
# control an LED on the reader
msr.led!(:red) # :green, :yellow, :all, :off
# get and set coercivity
msr.coercivity # => :high, :low
msr.coercivity = :high # :low
# more to come