This is one problem that isn't going to go away, is it? Perimeter security will always be the Achille's heel, particularly in countries generating the stowaways.
We only hear about the frozen corpses and the occasional successful stowaway. How many more cop out at the last minute or don't quite make it before the aircraft starts moving?
A few posts on here mentioned CCTV and sensors and I'm sure there must be companies working on precisely that now. Isn't it rather a lot to expect that you can put a monitor on the flight deck and build a constant watch of it into the pre-departure procedures? The remedy might just turn out to be a lot worse than the disease.
But what if you had a monitor on the flight deck and another on a bulkhead in the cabin, with one of the cabin staff assigned to watch it during the departure taxiing pauses? The flight deck monitor only switched on when the need is felt for a view of the cabin.
Isn't it Airtours that have the forward-pointing CCTV mounted underneath? I wonder what a little pod of three infrared cameras placed under the fuselage midway between the nosegear and the leading edge of the wings would cost. Combined with motion sensors in the back corners of the main gear wheel bays, a few hundred thousand dollars per aircraft perhaps? Ouch.
As for terrorists placing or carrying bombs into wheel wells, isn't that a bit far-fetched considering shoulder-held alternatives released from the perimeter fencing itself?