This answer mentions about several mobile ethereum wallet apps.
I am interested in building a mobile wallet app, and wanted to know how existing apps work.
Does anyone know whether any of these apps run an ethereum node in the mobile device? Or do all of them connect to an external ethereum node for obtaining information about the chain and send transactions?
If you are interested in building a mobile wallet, use a node on a server at this point.
If you are interested in playing around and learning something new and the challenge of getting Ethereum working on a limited-spec (mobile) device, talk to Bob Summerwill.
https://www.linkedin.com/pulse/porting-ethereum-mobile-linux-bob-summerwill
His talk on "Ethereum for Resource Limited Devices" @ Devcon 2 https://www.youtube.com/watch?v=S7jT7IWRVlw
Here's a random blog with a ton more links and resources on the subject from June '16: http://markspanbroek.github.io/2016/06/02/ethereum-light.html
The apps themselves do not run a node in the mobile device. Seeing as the chain is multiple GBs in size, there is no way for a (standard) mobile device to hold this datsa. Rather, each app has their own backend server that is hosting the node. This acts just as a node on your own computer, the difference being that many different addresses are pointing to it at any given time.
