Track your balance/limits/credits/data over USSD (Android 4.1+) or SMS requests and show changes in nice widget. Full history/statistics supported in Pro version. Background requests supported after call on schedule etc. If you use code like *100# for getting your balance you can easily configure piBalance to use this code.

And the following mobile operators supported out of the box:
Australia: Optus Lebara
Belgium: Base (KPN Orange)
Bosnia and Herzegovina: BH Telecom
Bolivia: Tigo
Brasil: VIVO TIM
China: China mobile China Unicom
Costa Rica: Kolbi I.C.E. Movistar
Finland: DNA Finland
France: Free
Greece: Vodafone
India: Vodafone IN TATA DOCOMO Aircell Reliance CellOne
Indonesia: INDOSAT
Ireland: Vodafone IE
Kazakhstan: Tele2
Kyrgyzstan: Megacom Beeline
Latvia: BITE
Malta: Vodafone
Nigeria: Nigeria Communications (MTN)
Namibia: MTC
New Zealand: Vodafone
Pakistan: Ufone (Pak Telecom Mobile)
Poland: Orange
Portugal: Optimus (Sonaecom)
Philippines: Globe Sun
Romania: Orange (MobilRom)
Russia: MTS Megafon Tele2 Beeline SCS UTEL Smarts BaykalWestCom Rostelecom
South Africa: Vodacom Cell-C 8.ta
Serbia: TElenor
Switzerland: Swisscom
Sri Lanka: Dialog
Tajikistan: MegaFon
Thailand: Dtac
Turkey: AVEA
Turkmenistan: CELL MTS
UK: T-mobile O2 Vodafone
Ukraine: Life:) Kyivstar MTS Beeline Utel
Uzbekistan: Beeline

kw: balance limits ussd widget check balance