Single-Spd (pedal) Chain Tensioner-Availability Check

my new build will be a 2-spd crank paired with a coaster-brake, i need a tensioner.

it's going to be a clean build & i don't want to modify a whole rear-derailleur, i'd rather find something like this, but not so costly: http://www.jensonusa.com/store/product/CG409Z16-Paul+Melvin+Chaintensioner.aspx

buy, beg, or trade for stuff...whatta ya got & whatta ya need?

 

Would their tensioner work ?
http://www.psyclestore.com/shopping_cart.php?sort=2a&osCsid=0ed4edc82723dc481cf95782c6563c58

 

looks like it might...thanks for that link