A BGP beacon is a compact BGP speaker that announces and withdrawls a beacon prefix at specific intervals. The behavior of this prefix can then be analyzed closely.
Zhuoqing Morley Mao's BGP beacon software is availble at http://www.routeviews.org/scripts/bgpd.pl-agg-0.04_03_03_17.tar.gz or http://psg.com/~zmao/Software/bgpd.pl-agg-0.04_03_03_17.tar.gz.