Even though we don’t see them in most devices, AAA batteries can be pretty darn useful, aside from powering remote controls and toys. Philips thinks so too, that’s why the Philips Xenium 9@9j has a AAA battery slot at the base. This is very likely the first cellphone that supports a AAA battery. It supposedly gives it up to three hours of talk time. It still has the standard lithium ion rechargeable battery, but the AAA is a backup.
It does add some bulk, but what is a backup worth to you? The 9@9j should be around in April. The technology is from the Israeli firm Techtium, and they are calling it Backupower. If your main battery goes dead, the backup battery takes over.