List of all available ARM+DSP processors for surveillance
As you mention other non-ARM options in the comments, here's a few:


Blackfin
Xilinx's Zynq (ARM+FPGA)
Altera also do a similar ARM+FPGA
Some of Freescale's i.MX51 processors might be suitable (ARM+co-processor, not a true DSP) - although I'm not sure if there's out-of-the-box surveillance software
And of course, there's always the PC+GPU option, depending on your power, cost, size, weight constraints