Heat oil in a saucepan large enough to hold your pipis, over medium heat. Add the onions, green capsicum, celery and garlic; and cook, stirring until tender, about 5 minutes.
Stir in the tin of tomatoes with green chillies, wine and pipis. Turn the heat up to medium-high, cover the saucepan, and cook for 5 to 8 minutes, or just until all of the pipis have opened. Remove from heat immediately.
Pipis are a New Zealand shellfish, you can use any kind of clam.