A Playstation on your cell phone?  The notion might not be so far-fetched. The latest news out of the Japanese electronics and gaming giant is that it’s “considering developing a cellphone-game gear hybrid” on Sony Ericsson phones.Once the superpower in portable music – the Walkman, launched about 30 years ago, was revolutionary and became one of the best-known brands of its time. Anyone who didn’t own a Walkman owned a knockoff. The Discman, which, as it sounds, played compact discs wasn’t as huge a hit,