(IDEX Online) - The Swiss watchmaker Bovet 1822 has crafted a bespoke pair of his-and-hers watches that double as the dashboard clock of the new ultra-expensive Rolls-Royce Boat Tail.The one-off handcrafted car is said to be the most expensive in the world, with an estimated price tag as a high as $28m.Bovet designed and made a pair of reversible watches, together with a dedicated aluminium and titanium mount. The wearer removes the watch strap and inserts the timepiece into the dashboard.Both timepieces feature a hand-engraved miniature of the Boat Tail, a 6.75-liter V-12 convertible with distinctive side-opening boat tail compartments in the rear.The car is widely reported to have been commissioned by hip-hop icon Jay-Z and singer wife Beyonce. Pics courtesy Bovet 1822 and Rolls-Royce Motor Cars Limited.