Provide a link to the relevant piece of legislation, or get thee hence back to the Trollery.
Very well - I'll make sure to use small words for you.
Herewith the link to
FAR Part 91 Sec. 91.21 effective as of 09/30/1963 - similar legislation can be found under each local authority worldwide (JAR-OPS 1.110 for Europe)
Any piece of equipment that has not been tested to RTCA DO-160 standards is considered unapproved for aviation use, and for the systems we're talking about, would therefore be considered Portable Electronic Devices (PEDs). Furthermore, "determination" of interference actually means that if the manufacturer has not certified the equipment to DO160 standards, it is up to the
operator to do so,
before it can be used. Switching it on and listening for crackling over the comms is not sufficient (nor even likely to find) interference of the kind tested for. The high power required to transmit between the aircraft and satellite can and has been shown to cause subtle interference in GPS avionics (including loss of GPWS), as well as compass, recording and other essential systems.
The Spidertracks system mentioned above is in fact prohibited from use in their own country of New Zealand by
http://www.caa.govt.nz/rules/Rule_Co...solidation.pdf - something that they're sure not to tell you!
Basically, unless a piece of electronic equipment has DO160 certification, it must be switched off as soon as the doors are closed - and please understand that this isn't just for commercial airliners, it applies to
every aircraft. Yes, you still shouldn't be using your mobile phone, even though it "seems" safe.
The difference is that in GA it is left to individual pilots to make the "determination", which is the weakness exploited by SPOT and the rest. Some caution should be exercised by good pilots (as everyone considers themselves) and make sure something is safe for use before introducing it into the aircraft. The reduction of GPS accuracy in your nav due to some gadget could have catastrophic consequences in IFR, and you wouldn't know because the interference is subtle.
So whilst these gadgets are a fantastic idea, and will undoubtedly improve aviation safety, make sure that the one you're using is part of the solution, and doesn't make the problem worse...