You'd need to walk an incredible 1,000 miles to unlock all the routes on the Pokéwalker that comes with Pokémon HeartGold/SoulSilver.
The Pokéwalker is a pedmoter-style accessory that comes with HeartGold/SoulSilver. You can store a Pokémon on it and as you walk around in real life your Pokémon will gain watts. You'll also unlock new routes, discover Pokémon and find items.
However, according to Bulbapedia, you'd need to walk 1,000 miles to get unlock all the routes in the Pokéwalker. That's assuming you take around 2,000 steps per mile.
So as if catching 'em all wasn't hard enough already, you now have to walk 1,000 miles as well! That's more than the distance from Land's End to John O' Groats!
Do yoy think you'll catch 'em all AND unlock all the routes?
You can watch our Pokéwalker video here.