The Coinomi wallet can support any kind of cryptographic currency because it adopts the model of a thin wallet.
A thin wallet will delegate most of the complexity to a trusted server, while still maintaining control of the private keys by using a deterministic key chain BIP44. It is different than SPV in that it doesn't need to perform any header or transaction merkle root validations (although it is optionally possible).
The advantage of a thin wallet is that it is light weight and can easily work with low-specs devices and consumes small amounts of network bandwidth. Some assets like Peercoin, CounterParty or Mastercoin can only work with this model because as SPV is not enough to validate transactions. The disadvantage is that it needs a trusted service to get the state of the network. A known attack for an SPV wallet is to hide transactions, in a thin wallet it is possible to al