The closest apps I know of are FL Studio, Orion, and Energy XT. Maybe Cakewalk Project V as well.
I use FL. It's a very good pattern sequencer, but the arp functions are different than those of the Motif. Still, several of my soft synths also have detailed arp and pattern functions, and Z3ta, amongst others, allow for the making of arp files from midi sequences.
Also there are add on vst plugins that are themselves arpeggiators. Commercial offerings include Sonicbytes ERA, while KVR-Audio also has a few free ones, including "stepchild".
In reality, I find the sequencer in FL to be much more intuitive and easy to work with vs the one in the Motif ES.
AJ
_________________________
AJ