Hi. An electric pump that can continually pump oil as effectively (i.e., generate as much pressure) as your mechanical pump would really require a hefty alternator, and I doubt it would accomplish any improvement in lubrication.
On the other hand, you may have heard of a pre-oiler -- and this would definitely improve engine life, since the greatest amount of engine wear occurs at start-up, before the engine's mechanical oil pump is able to circulate the lubricant. As you probably imagine, a pre-oiler only works just for a few seconds, before you start the engine and the mechanical pump can take over. Most of the pre-oilers I've heard of are actually spring-loaded, and use a compressed spring and piston to provide momentary oil pressure; but it isn't hard to imagine a powerful oil pump doing this instead.
But, even though it will minimize engine wear, it becomes a question of whether it's worth it. The way I look at it, Volvo engines don't wear very fast anyway, so it becomes a question of whether you want your engine to last 500,000 miles or 700,000 miles -- are you going to keep your car that long? IMHO, I feel that I get better protection by using a good (e.g., AmsOil) synthetic oil -- it begins circulating more rapidly than conventional oils, and has a very high film strength.
Bottom line -- unless you've got an engine with a reputation for high wear (early PRV V-6 camshafts, for example), I don't see that a pre-oiler is worth it.