Struggling in-flight entertainment house e.Digital is challenging some of the world's biggest gadget companies with claims that it owns vital patents for using removable flash memory in portable devices.

It's targeting brands such as Casio, LG Electronics, Olympus, Samsung and Sanyo in a legal scrap filed last March. But e.Digital says there's a far larger pool of companies currently infringing its patents, and has "identified annual U.S. revenues of more than $20 billion," from products using its technology.

e.Digital's biggest moments came inside the dotcom bubble, when speculation raised its stock price to the super-inflated highs common during the period. It got its start selling what it claims was the first-ever digital voice recording device with removable flash memory.