member login; view & pay pledges
CiviPledges can be set up so that
- a logged in contact can see their upcoming Pledges on their dashboard
- a contribution page can be set up as a self-service payments page

I set one up on the Drupal demo site so it should be there for a few hours before it flushes.

Dashboard is here 

Setting up a pledge is here 

The self-service payment is here but will only show if 'demo' contact has a pledge set up

If you need to add a Pledge to contact called 'demo' you can do so here

Hope that helps you.