Canon 1D series professional digital bodies have a voice recorder also, and the voice file has the same number as the image file, so an association can be made in a browser window without even playing the file.
I've also used the predecessor to the PDA... the nearly forgotten PAD. Instead of a stylus, it requires a pen, but a pencil will do, and is eraseable.
Since both Nikon and Canon have the ability to make folders, were I to shoot lanes 2 through 6, I would simply preload the PAD with folder names 100, 101, 102, & 103. Then, off to the pool deck to shoot. After shooting Lane 2, I'd enter L2 on the PAD right next to the "100". Change the camera to folder 101 and shoot lane 3. Enter L3 on PAD next to "101", etc.
By the way, the PAD is designed so that it can be clearly seen in direct sunlight, without any glare. It doesn't come with any preloaded software or games that would slow it down, and the batteries last indefinitely, so it's memory of the data, once entered, is extremely secure. It can be dropped 100 feet or more, and then stepped on, without any damage to the data. Admittedly, it is ancient techonolgy by today's standards, though.