http://www.boingboing.net/2009/09/28/here-come-the-airpor.html
says that a body stifles grenades so a body bomb isn't useful.

But a grenade acts largely via shrapnel which is stopped by a torso; but a body bomb acts via blast wave, especially on pressurized airplanes at 35kft. Since 250gm of unconfined
brisant explosive can down such a plane, 500gm (a pound) is
hazardous.

With a surgeon or a female more than a pound could be emplaced.

One has to wonder about the triggering system; some reports claim a text message might have been involved. Phones
are awfully tiny now! Interesting unexpected consequence
that they enable buttbombs.

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The third tactical shift is perhaps the most interesting, and that is the use of an IED hidden in the anal cavity of the bomber. Suicide bombers have long been creative when it comes to hiding their devices. In addition to the above-mentioned IED in the camera gear used in the Masood assassination, female suicide bombers with the Liberation Tigers of Tamil Eelam have hidden IEDs inside brassieres, and female suicide bombers with the Kurdistan Workers’ Party have worn IEDs designed to make them look pregnant. However, this is the first instance we are aware of where a suicide bomber has hidden an IED inside a body cavity.
http://www.securitymanagement.com/news/saudi-suicide-bomber-hid-ied-his-anal-cavity-006178

Also the Chechen women... fake pregnancy or boobs..