Colin can answer the question about including this as part of the standard Smartform database offer.
However, Betfair make the data available for free download in CSV format each night. You can see the full hitsoric file listing (going back to early 2008) at the link below:
http://www.betfairpromo.com/betfairsp/prices/
All file URLs have the same root, and each individual day's file follows a standard format with only the date varying. For example, SP data files for British racing win markets have the name "dwbfpricesukwinDDMMYYYY.dsv", where DDMMYYYY is the date.
If you've a reasonable grasp of programming it's possible to write a standard daily script to download the relevant SP datafiles and parse them to insert whatever variables you want from them in your database.