One of the central things to get mobile commerce (m-commerce) working is that customers, when asking for a product which might be sold out where they are right then, can find out if it is available somewhere nearby.
One step-stones towards this goal is what makes Milo tick behind the scenes: Milo taps into the real-time inventory data of real world brick-and-mortar shops and makes this data searchable.
Actually, the real work the Milo people did was talking a lot of big chains into their idea - and probably bonding them exclusively to them. This fact made Milo dainty enough for eBay. The auction giant bought Milo and now offers their service as an API to other developers which want to tap into their database.
Having Milo in-house will surely help eBay establish the base for what is currently forming as eBay now.