It's all about Antenna Engineering and Physics
This isn't a software problem ( integration time of the signal strength measurements - RSSI) in my humble opinion but a hardware problem associated with an unusual approach to realising the antenna. There are several radios in any phone - 2G, 3G, Wi Fi, GPS & Bluetooth - operating at different frequencies and the challenge is to optimise the receive and transmit performance of the antenna system without having to have say a pull out antenna - remember those on the early analogue units ! Optimisation takes account of the way the unit will be used - will it be used on a belt ( such as a pager) or in the hand & pocket/bag as with a phone.
Antenna systems are therefore carefully engineered components whose designs are tuned for best performance.
The human body - being a lump of salty water - will when brought near an antenna affect its' performance and therefore the antenna engineer has even more challenges to take this into account whether we are left handed or right handed. But they have all managed it pretty well up to now.
If you then - in a first - as far as I am aware - allow the antenna system to come directly into contact with a hand - and even more alarming allow the antenna feed point ( that part on the bottom left with the plastic seperation ) to be touched then it will de-tune the antenna and the signal will go down. No amount of software fiddling will change that - it's an antenna design problem in my humble opinion.
The solution requires a rethink of the antenna system design - so that perhaps form is not triumphing over function. Which may I realise be a problem in itself. What a nonsense to have to stick tape/blue tack/nail polish or even a rubber wrap around on your brand new 'leading edge' phone. As has been said it would be fairly easy for a test house to do a full test on the RF performance with and without a human ( or test equivalent ) to put this matter to bed for once and for all. I do agree with the chap who said it is basic physics - sadly that means there isn't an app to fix this ........