I have been using your wallet for 3 months and i have to say that it has worked beautifully for me on a Samsung S2 tablet - I was a bit hesitant to use the onboard exchange but I have had no serious problems so far - I was trading lots of Digibytes for Ethereum and although half a dozen transacations ended up unable to complete the coins were returned. - with complex hardware and software there are always going to be glitches from time to time but I applaud the quality, and the high level of security that Coinomi offers. 

I use the Electrum client which is embedded in Tails and it has a persistence option which is stored on the USB device with which you store the Tails OS on.

My experience using Electrum in Tails so far is a very positive one - The built in security of Tails/Tor and the rock solid Electrum client for me is the best balance of security and useability - I used to use a Trezor hardware wallet but found the constant upgrading of the firmware not to my satisfaction -  Interestingly the preferred way of using the Trezor is via Electrum, which supports Trezor.