Perfect for tech-junkie cyclists, SKYLOCK's solar-powered bike lock releases with a touch if you sync it with your phone. It tells you if someone's tampering with your bike (that's what the built-in accelerometer is for), lets you share your wheels with approved friends, and alerts your contacts if you have a serious crash. Twelve hours of sunlight translates to six months of frustration for thieves. $249

Bring tunes to the trail, but leave the batteries behind. ETÓN's Rugged Rukus sound system is durable and packs an impressive audio punch into two small speakers. It works wirelessly with your phone or audio device via Bluetooth and clips to your pack or belt with a carabiner. Keep it in sunlight for five hours to get eight hours of audio. A USB port lets you charge your player. $100

Light up the night with 250 lumens, and power another device while you're at it. GOAL ZERO'S Lighthouse 250 Lantern charges its LEDs with as little as seven hours of sunlight and can last 48 hours. When it's out of juice, use the hand crank to keep it running—a minute of elbow grease gets you 10 minutes of illumination. You can buy the lantern on its own ($80), but the seven-watt panels really make this kit. $160

With 2C's Solar Light Cap, you don't have to carry a headlamp and batteries in addition to a hat. The flexible solar panel on the brim charges all day so the ultra-bright twin LEDs can light your path after dark. A charge gets you three hours at full power; on a dimmer setting, the cap will glow all night. $28 to $60, depending on style