#CrazyIdea: smart, inflatable kayaks. The pump is built in. Push a button and it inflates or deflates the kayak, so you could easily put several in the trunk of your car. The kayak also has a waterproof mount for a smartphone, keeping the screen aimed at the paddler and the camera out at the river (or other body of water). Have software that tracks your location on the water (and perhaps that of the other boats in the crew), that records interesting things that happen at the front of the boat, and can identify wildlife. Perhaps build in some game functions as well, such as a visual scavenger hunt, bumper boats, or a Guitar-Hero like game where everyone has to paddle the same way at the same time.

Additionally, here are some freebies for kayak/canoe rental agencies: give people nets and reward them for collecting litter on the water. Perhaps with coupons for a nearby eatery. Such a restaurant partnership could be profitable, as after people paddle for an hour or two they're likely to want to eat. The restaurant could also provide coupons for the boating experience.