There is a good chance your engine doesn't even have frost plugs. The stick on ones are OK as long has you don't have to actually heat anything - 250 watts max. I put a Frostheater in my '05 Passat. http://www.frostheater.com/
The stick on ones can fall off and cause a fire. The coolant heaters are the best because they give instant or almost instant heat in the winter. VW has an OEM one and frostheater makes aftermartket ones.
Since your profile says looking, I assume you want a new car. I saw a similar post elsewhere for OEM coolant heater with different info, here is some more info:
VW# 1km 198 062 is the OEM retrofit coolant heater kit for manual transmission 2009 Jettas. I assume that it will probably work on 2010 Golfs and Jettas. VW# 1km 198 062 a is the kit for DSG transmission. I am told that they are interchangeable but there may be a small difference in fitment. It appears that the exact part number is a European special order part which costs about $450! An alternative may be the part for older cars 2006 Jetta, VW# Jnv 198 006 a. It's a Calix 550w heater. I don't know if it'll fit the new 2009-2010 TDI.
It would take forever for a freezeplug or oil dipstick heater that it would basically do nothing. Frostheater is cheaper but it's bigger and faster but doesn't fit like the OEM does. VW sells a 3 prong outlet that fits into the front grille.
VW TDI forum, Audi, Porsche, and Chevy Cruze Diesel forum
A forum community dedicated to Audi, Volkswagen, Porsche, and all turbo diesel owners and enthusiasts. Come join the discussion about performance, modifications, troubleshooting, TDI, maintenance, and more!