I understood that meshlium was a router that would talk to a raft of different communication devices. It doesn't care what system is standing behind that device. Since Arduino can use many different communication devices, it shouldn't be a problem but I would not have thought meshlium was a good idea for a personal project as you probably only need one method of communication.
The flow sensor looks much the same as mine, a hall-effect device and you won't need any libraries for it.
This link might be useful