Using multiple knots in rope to provide an action-based timed release mechanism can be very effective for certain types of self bondage/torture.
This method can be visualized by imagining yourself bound standing, with your hands secured above your head. The handcufs around your wrists are attached by rope to an eyebolt well above your reach. The end of the rope that is attached to the handcufs is secured by a series of knots, for example, 50. In order to release yourself you must untie 50 consecutive knots (and then go get the key, of course). Depending upon the tightness and complexity of the knots, this can take quite some time. As the pain that your torture of choice is supplying increases, the knots can be even more dificult to undo (the more frantic you get, the less coordinated you become).

              O    <--- - -eye hook in ceiling
              |\    <--
              |          |
              |          | - -rope hanging down
free       |          |
end ->  \|     <--
            {#}    <--
            {#}         | - -lots'o'knots 
            {#}    <--
             O     <--- - -loop in rope to slide your handcufs through
For example, for a self-induced bengay session, set up your rig as outlined above. Attach one end of your handcufs to one wrist and slide the yet unused side of the handcufs through the loop. Squeeze a bunch of bengay into your free hand. Quickly now, slather the bengay on the areas of interest (cock, balls, pussy, bung...). Before you loose your nerve (and your delicate little genitals start to glow), get that free wrist locked into the other side of the handcuff and prepare to squirm.

Use your imagination. I'm sure that you can come up with lots of variations on this theme.