Customers of MyPedals.com will be able to place their order by phone or online by 2pm for delivery by 5.30pm.
"The majority of deliveries will be made by cycle courier," said store founder Dan Davidson. MyPedals.com opened in 2010.
Deliveries will cost £7.50, with free delivery for packages costing over £100.
Customers also get notification of where their ordered products are in London, with real-time, street-level tracking via couriers packing location-aware apps.
Davidson said the service would be a boon for those unfortunate enough to have key kit stolen during the working day:
“If someone steals your lights, it’s no longer a matter of utility. Cyclists have enough to put up with, without losing the things upon which their safety relies.”
The same day courier service operates to locations in Central London and Canary Wharf.