this looks to me like one of those security things that can only work because it isn't used widely. Won't a carrot defeat this? If adoption becomes widespread, the trick will be known and therefore useless.
This is also likely to enrage the attacker to the point where he kills his victim.
And walking around with plastic all day is likely to cause infections.
Regarding infections, women walk around all the time with tampons/birth-contol devices, etc. in and infections are not a concern for most as far as I know.
Though I do agree that if it became widespread an attacker would simply check first.
Tampons are changed out relatively frequently and are not generally worn every day. Self-applied birth control devices are not generally worn all day, every day -- there is something just a little bit more predictable about opportunities for voluntary sex than there is for sexual assault.
There was a past where IUDs and tampons (not even just high-absorbency, but the materials used for certain ones...) caused TSS and more, and the risk factor is still kinda there, but nowadays it's almost unheard of. And just keeping something in a vagina doesn't mean it's about to turn into a toxic breeding ground like it did in the past. Not that I support this condom much, but it's probably not unimaginable for a woman to keep it inserted for most of the day if she wishes to, no worries about TSS or whatever else.
http://en.wikipedia.org/wiki/Date_rape_drug
"flunitrazepam, also known as Rohypnol or "roofies""