Turns out it wasn't a National Instruments product:
http://www.dataq.com/products/startkit/di194rs.htm
This is a $25 data acquisition system that could be good for a project of this scope, or for other projects. They even have a link with Science Fair Ideas.
Could even be free:
"Science Fair Project Submission Form
DATAQ Instruments, Inc. is proud to offer free DI-194RS Data Acquisition Starter Kits to qualified students grades four through twelve for use in their innovative and exciting science fair projects. DATAQ Instruments will give away one free DI-194RS per month (on average) to students for use in their science fair project. All we ask is that you send us a summary and photo of you and your project at the science fair that we can place on this website. Fill out the application form below for consideration (all fields required and will be validated)."
Here is a link for a frequency to voltage unit. With a little EE work, you have a Tach to connect to the Data Logger above:
http://www.national.com/mpf/LM/LM291...;20Description
NOTE: Don't use a hotmail account to sign up for a "free" sample as they charge several dollars for shipping and handling.