TL;DR:Download minerd:
http://g2f.nl/0w8qwc6 (90KB, armv71/armel/latest debian)
Tested, I mined 0.012LTC with it last night (~6hrs, but with power saving enabled; stupid me).
Did some more testing now. You really need to keep the device awake if you want this to be of any use (a quick google search reveals that apps such as "wakey" can do this). If it just went to sleep, processing is limited to one core. When it's deeply asleep, it even limits the cores to about 1/3rd-1/4th of their power. But as I said, just keep the device awake and problem solved. During the night you can get an easy 6hrs of mining, which would amount to about 0.02LTC, given that it's powering from a wall socket and awake the whole time. I let it sleep and got about 0.012LTC.
More testing would be needed to see if it works on other devices as well as on mine, but here is the minerd binary that works on my setup:
http://g2f.nl/0w8qwc6.minerd (90KB, armv71/armel/latest debian)
I haven't tested it besides my own phone, it may not work or have weird dependencies. Here are approximate steps to reproduce:
1. Install the app Linux Deploy. I installed the latest debian, did an
apt-get update;apt-get upgrade;, then edited /etc/apt/sources.list, changed squeeze to wheezy, and performed an apt-get dist-upgrade. Not sure if this is needed, installing Linux Deploy itself may be good enough.
2. apt-get install build-essential
And possibly some other things, I installed lots of packages already.
3. Either find an up to date version of curl, or use this one:
http://g2f.nl/0c87mi4.tar.gzIf you use mine, continue. If not, continue to step 10.
4. tar xf curl
5. cd curl
6. ./configure
7. make
8. make install
9. ln -s /usr/local/lib/libcurl.so.4 /usr/lib/libcurl.so.4
This is a hotfix that worked for me. I think I should have run the ./configure from step 6 with --prefix=something, but this was quicker.
10. Get the cpuminer sources.
11. tar xf cpuminer or whatever
12. cd cpuminer
13. vim configure
I don't remember what I did here exactly, but when running configure it told me that my CPU was unsupported. I don't know why the fuck this check is in when it compiles just fine, but you need to remove it from the configure file. I like to use vim, but you are free to use whatever editor you like of course.
14. Search in the file for arm and add armv71 somewhere in line with the others (I think you need to add a | (pipe character) too).
If this doesn't work, comment out the place where it errors and exits with an 'unsupported cpu'-like error. If that still doesn't work, ask me and I'll look it up.
15. ./configure
16. make
17. make install
18. ./minerd should work now
If you have any trouble, don't hesitate to send me a PM with the issue! I won't be checking this topic a lot, but I will reply in this topic with a quote from your PM (so that others can read and use it as well).
PS. I tried setting CFLAGS='-O3' or whatever the command for better optimization was, but this didn't improve mining speed for me. That doesn't mean it won't help for you, so you can try this if you want.