“Loving the Ocado iPhone app – just did the shopping on the bus,” one Londoner enthused on Twitter last week, just hours after the online grocer launched on the Apple smartphone.

The “Ocado on the Go” app stores the grocer’s 18,000 products on users’ phones rather than relying entirely on constant network coverage, so losing connection mid-shop doesn’t matter.

Ocado co-founder Jason Gissing described the launch as “the first step of a journey that will eventually see Ocado available on several digital platforms”.

Indeed, the iPhone is far from the only handset that retailers need to be able to reach their customers on. But developing applications for each of the growing list of mobile platforms available to shoppers is one of the challenges online retailers now face. Ocado may be the first grocer to start tackling this challenge, but it won’t be the last. One to watch is Tesco, which is opening up its databases to third-party programmers.