I've used several - Cateye Astrale, Cateye Mitey 3, a low end performance Axiom, a Polar 150, and a Polar 720 (the new toy). For features/performance//reliability vs price, I suggest the Cateye units. The Mitey is on my commuter/tourer, and has been maintenance-free. Just take some care with routing and zip-tying the speed sensor cable to the bike.

The Astrale has 2 features you may want - cadence, and a rear-wheel speed sensor, which lets you see how "fast" you are going when the bike is mounted on a trainer.

Wheel calibration data is usually close enough (within a few %), a quick roll-out test on a flat surface will get you an exact number. Cateye has copies of all their manuals on-line, so you can answer the "how do I do that?" after you've misplaced the manual.