Standing Wave Ratio is a measure of how much of the signal that you trying to fire out of an antenna is being reflected back.
A low SWR is an indication that most of your transmitting power is actually being delivered to your antenna.
I find it so hard to believe that anyone would have designed a hand held radio that lets the antenna come in contact with the human that's holding it.
Its bad enough to have capacitive coupling (Where the plastic casing is thin enough to allow the signal to be transfered to the user).
If you think about it most hand held radios (walky-talkies) have their antenna's in the end of a stick. Its only as phones have become small that this stick has become small too and as such produces concentrated RF emissions right next to your head. As a result manufacturers mostly place the gsm antenna at the bottom of the phone.
Most antennas have a hot end (usually the tip) its high voltage low current and a cold end (usually the base) low voltage high current.
Is it purely down to detuning or just a plane short circuit?
I've seen demo's on youtube that show an actual call being dropped, no amount of s-meter recalibration is going to fix that.
It would be interesting to see if the part of the side antenna that is (so say) shorting is the hot end or the cold end. If its the hot end then the problem may well be caused by the bluetooth or wifi radio actually swamping the gsm radio receiver. This could be fixed in software by detecting that the phone is being held (somehow) and turning off the wifi or bluetooth whilst in a call. This could be made to come into play only in a poor signal area.
(sorry to those of you in the know. Being a HTC user I'm not sure which side the wifi / bluetooth is on)
If its the cold end that is shorting then the best answer is a bumper. I'm sure it won't take long for these to be appearing very cheaply in ebay.