Attention, entrepreneurs! Great (?) tech ideas!

So I subscribe to a mailing list called Idea A Day, which is noteworthy for offering reader-submitted "great ideas" that rarely have merit. Cases in point are the occasional tech-related items, which I'll post here as interesting ones come up.

Anti-hearing aid

Idea: "Produce an anti-hearing aid that would function in the opposite way to a traditional hearing aid. When turned up sounds would be muted, allowing the user to reduce the volume of, for example, an irate boss, an elderly relative's television set or a next door neighbor's drum rehearsals."

Comment: Well, nothing bad with the idea, but it's old. The latest incarnation is electronic noise-cancelling headsets, which have been around for many years. 

And before that? Try this, would-be inventor, before you rush to patent your idea: earplugs. Seems this clever invention was known even to Odysseus, who used beeswax earplugs to drown out the deadly song of the Sirens. 

Cold water bottle

Here's a real flight of innovation:

Idea: "Invent a cold water bottle - the opposite of a hot water bottle - that would help keep the user cool during oppressively hot nights."

Comment: Hey, genius, try this: Put cold water in your hot water bottle! Instant invention!

L-mode

Idea: "Add text messaging functionality to landline telephones such that they can send and recieve messages to and from mobiles and other enabled domestic telephones."

Comment: When this suggestion appeared on the mailing list in 2001, the service already existed. One form was "L-mode", a land-based equivalent to NTT DoCoMo's then-new "i-mode" cell phone-based text and Internet service sweeping Japan. L-mode phones were targeted mainly at older folks, letting them join in some of the text action without having to leave the comforting presence of a white plastic desktop phone.

Okay, nothing funny about that. I only point out that it's a fine idea, yet seems to have flopped in Japan; L-mode never caught on, and NTT stopped accepting new application in 2006.