Even though the sensor readings always appear eventually on my '09, sometimes they take two to three minutes to appear, sometimes they take ten seconds.

They seem to appear on the display more quickly if I start off very gently, getting above 30 Km/h but staying below 40 for the first few hundred metres.
On my '10, the readings consistently appear on the display within 100m of moving from standstill - sometimes less. By default, the readings are present before the bike has even left my driveway.
They must have a centrifugal switch of SOME kind.
Thing is, though: where on earth do you slot batteries into the sensors?
I've gotten up close and personal with all four sensors on both my bikes, having changed tyres and rims for various reasons.
Taking a close look at the RDC sensors, they appear to be a one-piece moulding, with all internal electronics 'potted in' to the sensor body.
They have no conventional 'cover' of any kind behind which batteries could be hiding - just a tiny hole on the sensor body which, I presume, is the orifice which leads to the actual air-pressure sensor.