its kind of scary if one of the developers installs a malware to steal your coins. you would never know. or maybe the dev got hacked and didnt even know someone installed a trojan to steal coins sometime in the future. thats why is it worth it to go with mainstream wallets vs not so mainstream?
Use open source wallets such as Bitcoin Wallet by Andrease Shildbach. Check the code before installing or ask a person you trust to do it. After that, you can compile and build an APK file yourself. Don't update after that unless it is a ciritical update.
maybe its better to understand how to generate your own addresses by coding it urself.
You can use a dice to create a private key. For converting private key to public key, you will have to use any script which does it. For example, bitaddress.org. Download it and use it in an offline machine(mobile or pc).
That's what I suggested somewhere else. Roll a 6 sided casino grade dice, about 100 times.
If you get a 1, write down 0.
If you get a 2, write down 1.
If you get a 3, write down 2.
If you get a 4, write down 3.
If you get a 5, write down 4.
If you get a 6, write down 5.
base6 number = 3315135445300124430102440020244024024200400400022442224420424444024020024240204
40440400202424020222
convert to base 16 = 8E85A30B4276949DBFBC8771EDC4BCF98B66785E68D22D162CE6E8D69D50819B
which is:
Private Key: L1zkkHQDDtQTDRtZQwJJxATFrDMTstGxMsKhxySaa4vqEFtwtnmd
Bitcoin Address: 16PYKf15c4kH7jYM4MTwQCgcmYuviLxGxB
You could also use 16 sided dice, there's one that's even called and labeled "hexadecimal dice".
Another way:
Another way to do this, for "perfect" entropy calculation is to roll six-sided dice and write down bits. Then convert those directly to a private key.
If you roll:
1: write down "00"
2: write down "01"
3: write down "10"
4: write down "11"
5: write down "0"
6: write down "1"
Yes, you only get one bit when you roll a 5 or 6, two bits for everything else. Stop when you have written down 128, 160, 192 or 256 bits (whatever your preference is). If the dice rolls are perfectly random, so will your resulting binary string.
