Yes, they do, but whether they're portable enough to carry around? Many are low W though.

Linuxdevices.com is a good website to find out about (embedded) devices running Linux.

Also, it might be important if the device has hardware MPEG2/MPEG4. Then you can also use it to record from a source, and then play it on NIT. That way, one could in theory record something from TV, convert it, and watch it later on the NIT. No need for DVB-H.