Markit's CDX.EM tracks the composite performance of emerging (bond) markets. If you pull up equity charts, you will notice a close correlation between the two w/bonds typically telegraphing moves in equities.
Right now, the concern is whether or not China has created over-capacity in infrastructure development. Based on recent Baltic Dry Index data, cargo ships full of steel, copper, iron, and coal have dropped off significantly.
Shorting emerging markets is also a play typically associated w/a stronger dollar/lower bond yields.