I don't know about this. If you read between the lines in their FAQ page I get the feeling that this is "snake oil". I love the louder the songs, the faster the charge FAQ. Not to mention they recommend the installed battery version over the "radio/headphone charge.
Here is a copy from their site:
Frequently Asked Questions
Does the cable charge my device continuously?
With the optional battery boost feature, the device will output power continuously, in the non-battery boost mode the Inflight Power cable uses an internal trickle charger that takes 3-5 min to fully charge, then outputs power to the attached device (phone, music player etc). It does this repeatedly; batterires are recommended for better perfomance.
Does the charger work better with certain seat music channels or audio selections?
The Inflight Power cable works well on loud forms of audio (Marachi), music channles do better than talk channels, and be sure the volume is adjusted to maximum. Not all audio channels will provide sufficient power. Ask your flight attendant if they provide a "Charging Tone" audio channel, this is a saturated audio recording provided by Inflight Power to the airlines to ensure good performance.
Can I plug-in and use the cable before takeoff and after landing?
Yes, the Inflight Power cable is FCC certified and does not emit radio noise. You can use it anytime. Note: some flights do not turn on the seat audio system or reset the volume of the audio after take-off; so for optimal performance check the audio levels after take-off to ensure they are set to maximum.
Can I plug-in to other audio sources to get a charge?
Yes, the Inflight Power cable can operate using battery power and no audio input, or can operate on headset output signal from a laptop, an iPod or other audio source.
How do I know the Inflight Power Cable is working?
A led/light within the cable's plastic case will glow when the cable is ready to charge the attached device.
CABLE TEST PROCEDURE - To test the device with no battery boost
You can test the product using just an IPOD,
1) simply download our power tone Right Click to download Power Tone Clip
2) download this file to your IPOD, using ITunes etc.
3) select Setting>Repeat = One from the main IPOD menu, this will loop or repeat the song played.
4) plug the Inflight Power Cable audio plug into the IPOD’s headset jack.
5) select Music>Songs>500HzPowerTone from the song list, play this song (really a tone not a song)
6) after 90 seconds of playing the power tone above, the Inflight Power Cable LED light will glow and you can plug the USB IPOD attachment into the IPOD bottom connector or plug-in a Blackberry USB cable and charge.
Can I use the USB cable that is included with my mobile device?
You can if the USB cable is a charging cable, this can be determined by plugging the USB cable into a PC or laptop USB port (computer turned on), and attaching the associated mobile device. If the mobile device indicates that it is charging then the cable can be used with the Inflight Power cable. Note: some USB cables require software drivers to operate and require the attached device to first sync before allowing the cable to be used for charging, these will likely not work with the Inflight Power cable. See our product section to purchase a charging USB cable or tip for best results. Not all USB devices can charge using the Inflight Power cable, see the products section for more information on tested devices.
-Seth Williams
San Francisco, CA