So, I'm running the latest app, 4.17. I have a few questions that I hope someone can answer, as I am unable to find good answers googling.
Tips will be provided for good answers!
1. Since the app creates new addresses for every change address and every receiving address, do I need to backup the wallet more than once? If so, how often?
No its HD[1], thus a single backup is enough.
2. There is the possibility to add a "trusted peer". I understand that this can be my own full node, running on a computer I have control over, but I'm thinking that there might be a point in entering a well known and well connected node. Is that a good idea and if so, where can I find such a node?
I keep passing this list of nodes around for people running bitcoin core/qt to sync faster. They are well known in that regard and usually well connected. There is also the site called bitnodes[2] which might help selecting a node of your liking.
As regards whether this is a good idea or not I dont think it should be a problem. A malicious full node could feed you bad information, but the client is checking them anyway. Thus worst case would be that you do not get notifications about your transactions and/or your transactions do not get relayed.
last updated 2015.01.11
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IP - location - owner[1] - speed - info/stats page[2] - testnet
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84.200.34.113 - Freinsheim, DE, EU - Newar - 1000 mbit/s - yes - no
185.45.192.129 - Amsterdam, NL, EU - anon - 1000 mbit/s - /node.php[3] - yes
94.23.146.127 - NL, EU - anon - 200 mbit/s - /status - no
213.165.91.169 - Germany, EU - shorena - 100 mbit/s - yes - no
191.236.50.217 - Virgina, US - grue - 100 mbit/s - no - no
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!!The following nodes have been unreachable at the time of the last update and might[5] be down!!
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eldinhadzic.org[4] - LA, USA - eldinhadz - 1000 mbit/s - no - no
50.7.68.180 - New York, USA - Newar - 100 mbit/s - yes - no
5.9.24.81 - Germany, EU - zvs - unknown - no - no
178.79.173.71 - United Kingdom, EU - zvs - unknown - no - no
107.155.104.194 - Dalls, USA - zvs - unknown - no - no
106.185.32.195 - Japan, Asia - zvs - unknown - no - no
94.242.57.173 - Russia, Asia - zvs - unknown - no - no
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[1] refers to a bitcointalk.org username or anon if requested
[2] same IP, port 80 or path/port given
[3] work in progress
[4] IP is 173.236.158.177
[5] or reached max connections at the time of testing
3. Should I enable BIP70? Is there any danger doing so?
It can speed up a payment process which is nice on a phone. I dont see any dangers here as well. More about BIP70 can be found on the bitcoin github[3].
4. Any other things I should think about?
Phones get lost, IIRC its hard to restore the wallet if you do not have another phone that can run the app. There was a post by someone with this problem here I think. If you have an old phone, consider keeping it around for this instead of gifting it away.
Phones get stolen/robbed, keep only what you would keep in a regular wallet.
[1]
https://github.com/schildbach/bitcoin-wallet/issues/181#issuecomment-64903274[2]
https://getaddr.bitnodes.io/[3]
https://github.com/bitcoin/bips/blob/master/bip-0070.mediawiki
