From the BBC article: "Stefan Gulas has developed a system that amplifies the effort you put in by a factor of 50, meaning you can accelerate quickly and maintain high speeds with very little effort"

I get the sense the "effort amplification" bit is intentionally worded to be utterly misleading. He's more likely saying "2% of the energy used by the bike is coming from you, 98% is coming from the battery." So the pedaling charges the battery slightly, but it's almost negligible.

In fact, this sort of thing already exists and there's a name for it, it's an electric moped. (only not a street legal moped since it's speed is similar to middle range electric motorcycles) You can pick up an electric moped now for under $1000, if that's the sort of thing you think you might be into.

http://www.metaefficient.com/electric-bikes/the-best-electric-scooters-of-2008-a-review.html