A company called J.L.D. Guitar Research created the guitar Bridge Doctor around 1985. Basically, the device attaches to the underside of the guitar bridge. An adjustable rod extends from the base of the bridge doctor to the tail block. For a new instrument, the rod is adjusted so as to just touch the tail block; string tension then rotates the Bridge Doctor ever so slightly so that firm contact is made between the rod and the tail block. The device then acts as the ultimate interior brace - using leverage, the Bridge Doctor transfer the string tension to the end block, thus relieving the stress on the top of the instrument. This not only arrests the distortion of the face that is inevitable on pin-bridge type flat top guitars, but it actually improves the sound by allowing the top of the instrument to vibrate more freely.
The J.L.D. version can be adjusted (gradually, over a number of months) to actually restore the tops of older instruments to flatness. My understanding is that most Breedlove Guitars come installed with the device. I am familiar with one instance, when an experimenter successfully eliminated all of the original top braces on a dreadnought guitar, then installed only five short braces radiating from the Bridge Doctor. This experiment was done over 5 years ago and the last I heard, that guitar was still playing fine with no face distortion. I personally endorse and highly recommend the J.L.D. product.
My version (see diagram below) is NOT adjustable, but is glued into place permanently (with a hardwood dowel through the face and bridge) in order to prevent, or arrest, the distortion of the face. I first install it without the glue, to adjust it for position, then pull it out, glue it up and finish the installation. The dowel is cut off and sanded flush with the bridge and stained, so it barely shows - if at all.
I have used the device successfully in some instances to convert tailpiece equipped flat tops to a pin bridge, but mostly, I use it to prevent any further distortion on older guitars which already have pin bridges.
Here is one a friend installed in a ukelele.