Actually, there isn't. The cloven tongue, spoken of by the prophet Joel and described on Pentecost day in Acts 2:
2:4 And they were all filled with the Holy Ghost, and began to speak with other tongues, as the Spirit gave them utterance.
2:5 And there were dwelling at Jerusalem Jews, devout men, out of every nation under heaven.
2:6 Now when this was noised abroad, the multitude came together, and were confounded, because that every man heard them speak in his own language.
2:7 And they were all amazed and marvelled, saying one to another, Behold, are not all these which speak Galilaeans?
2:8And how hear we every man in our own tongue, wherein we were born ?
If it can't be understood, its not from the Holy Spirit, and its a fraud.
Acts 2 clearly debunks the 'speaking in tongues' rumour. If it can't be understood, it isn't useful for anyone.