I would like to check a Nokia N8 for possible software that might send any kind of data without my consent.
Is there a specific tool to achieve this? Are there specific techniques?
Do you want to prevent the phone from sending data for billing issues or are you interested in protecting confidential information?
There are software and hardware tools to analyze the content on the phone from the free Symbian OS SDK to Device Seizure v4.5 which starts at $1,795.00 (US). The more sophisticated and specalized the tool the easier it will be to come to a clear conclusion regarding the software and data usage patterns.
For billing issues the easiest technique is to monitor your own data usage and compare your recorded data usage to the ussage you are billed for. If the two are not highly similar then there may be a problem. Ask your carrier or retailer about expected background data transfers.
For confidential data the most secure technique is to not put confidential data on the phone. Beyond that it depends on the size of the data and the length you are willing to go to protect your data.
Have a look through this paper http://www.dai-labor.de/fileadmin/files/publications/573605840_symbian_malware.pdf
It is about malware analysis on Symbian !
Also there are plenty of techniques discussed in this book http://www.amazon.com/Mobile-Malware-Attacks-Defense-Dunham/dp/1597492981 you might want to get a hold of a copy and read through it !