Dawn gives it to you on your way to Hearthome City after you have gone down Cycling Road.
yes
You get the Poketch Dowsing Machine from Rowan's assistant on Route 207 after getting the Bicycle. This is on Pokemon Diamond and Pearl by the way...
Use the Dowsing Machine at Mt. Mortar.
This was categorized in Pokemon Diamond, Pearl, and Platinum, so here is where you can get Rare Candies in those games. Pokemon Diamond and Pearl: Route 207 (With Dowsing Machine), Route 214, Route 218, Route 223, Route 224 (With Dowsing Machine), Route 225, Route 226 (With Dowsing Machine), Route 228, Route 230, Old Chateau, Wayward Cave, Mt. Coronet, Mt. Coronet (With Dowsing Machine), Solaceon Ruins, Valor Lakefront (With Dowsing Machine), Snowpoint City (With Dowsing Machine), Victory Road, Victory Road (With Dowsing Machine), Victory Road (With Dowsing Machine), Stark Mountain, Veilstone Galactic Building, and Floaroma Meadow. Pokemon Platinum: Route 207 (With Dowsing Machine), Route 210 (With Dowsing Machine), Route 212 (With Dowsing Machine), Route 214, Route 216, Route 218, Route 223, Route 224 (With Dowsing Machine), Route 225, Route 226 (With Dowsing Machine), Route 228, Route 230, Old Chateau, Wayward Cave, Wayward Cave, Mt. Coronet, Mt. Coronet (With Dowsing Machine), Veilstone City, Snowpoint City (With Dowsing Machine), Victory Road, Victory Road (With Dowsing Machine), Victory Road (With Dowsing Machine), Survival Area, Stark Mountain, and Floaroma Meadow.
a machine that helps you find items.
You can find one at Route 210 (with Dowsing Machine), Route 228, and Iron Island.
Use your dowsing machine around Lake valor and you should find it neartwo homes
In Pokémon Red, Blue and Yellow you can find it in Silph Co and the Pokemon Mansion. In Pokémon Gold, Silver and Cristal you can find it in Kanto at Route 12 and 13. In Pokémon Ruby, Sapphire and Emerald you can find it at Route 119, 123 and 124. In Pokémon FireRed and LeafGreen you can find it in Rocket Hideout, Silph Co, Silph Co and the Pokemon Mansion. In Pokémon Diamond and Pearl you can find it at Route 209, 213 (With Dowsing Machine), 217 (With Dowsing Machine), 228 (With Dowsing Machine), Snowpoint Temple (With Dowsing Machine), Victory Road, Stark Mountain (With Dowsing Machine). In Pokémon Platinum you can find it at Route 209, 211 (With Dowsing Machine), 213 (With Dowsing Machine), 217 (With Dowsing Machine), 228 (With Dowsing Machine), Fuego Ironworks, Veilstone City (With Dowsing Machine), Victory Road, Stark Mountain (With Dowsing Machine). In Pokémon SoulSilver and HeartGold you can find it in Johto in the Union Cave (With Dowsing MCHN), Whirl Islands, Mt. Silver and Dragon's Den and in Kanto at Route 12, 13 (With Dowsing MCHN), Digglets Cave (With Dowsing MCHN). In Pokémon PokéWalker you can find it at the Treehouse (4500+ steps) In Pokémon Black and White you can find it at Route 18 (With Dowsing Machine), Victory Road and Village Bridge. In Pokémon Black 2 and White 2 you can find it at Route 2, 3, Driftveil City, Route 22, 23, Reversal Mountain (With Dowsing Machine), Seaside Cave.
use your dowsing machine
You can get one in Solaceon Ruins with the dowsing machine app on the poketech.
You can obtain potions and other helpful items for you and your Pokemon. You'll also need to use the dowsing machine in Pokemon Diamond, Pearl, and Platinum to find this lady's Suite key because she lost from watching the scenery around her.
The places listed are only what I could find, and you should bare in mind that these are not necessarily all the places you can find Rare Candies. The Dowsing Machine appears to be of great use when it comes to obtaining items, so I recommend you use it frequently.JohtoRoute 34, Violet City, Ecruteak City with Dowsing Machine, Olivine City with Dowsing Machine, Mt Mortar with Dowsing Machine, Tin Tower, Whirl Islands with Dowsing Machine, Mt. Silver with Dowsing Machine, Shining Lighthouse.KantoRoute 27 and 28 with Dowsing Machine, Vermilion City Fan Club President, Cinnabar Island Dowsing Machine, Indigo Plateau with Dowsing Machine, Cerulean Cave with Dowsing Machine, Victory Road.ShopsJohto: Battle Frontier, Pokéathlon Dome.Total of 16, not including the shops.