i found this

[img]http://education.ti.com/images/rightcolumn/products/apps/scitools84_L.gif[/img]http://education.ti.com/educationportal/sites/US/productDetail/us_scitools_83_84.html

think they have already come up with a great way to explain significant figure embedded in 
Science Tools App for the TI-83 Plus and TI-84 Plus Families.

think forget it, Texas [img]http://education.ti.com/images/webelements/pix.gif[/img] have a great teaching strategy through use of their calculator.

in my opinion, this is the best way.  Any way i can make one calculator emulator using EJS from  open source codes in Javascripts etc ?