Many bracelets exist already here on thingiverse (one of my favorites is MakeALot's: http://www.thingiverse.com/thing:7354), but most are rigid shapes. This design bends smoothly around the wrist and clasps in a secure, yet smooth and unobtrusive way. The intent is also to show how any bas relief design can be turned into a unique flexible bracelet. The pattern shown here is simply a pleasing combination of sinusoids.

There are several levels of personalization available, depending on how much effort you want to put in. The easiest is to scale the file to fit your wrist (the current design has a circumference of 17.1cm with two pieces). Any number can be joined to form a larger circle. By adding M1 commands to the Gcode you can switch colors at different heights to highlight certain features (as shown). And finally, you can modify the OpenSCAD file to turn your own design into a segmented, flexible bracelet.

I use Multiply to print two of these at once. The initial z-height must be well-calibrated and make sure that "infill begin rotation" is zero in the fill section of SF, so that the fill lines run the length of the bracelet for strength. A single layer is meant to form the backbone of the bracelet, so if your layer thickness is vastly different than 0.3mm, you may have to adjust the T parameter in the scad file. I'm not sure about PLA, but ABS has plenty of strength and flexibility to keep this bracelet from wearing out.

The base shape in this case was created in Matlab (wiggly.m), which will also probably run in Octave, though in either case you'll need to download surf2stl from the file exchange. Feel free to modify this to a different mathematical shape, or start fresh from any other modeling approach.