A water/ice pokemon could provide permanent drinking water but the only kinds alive are relicanth and staryu. Maybe castform when it rains. (Oh wait.. i forgot the fossils)
To prevent nuclear infection I suppose Cleffa could use aromatherapy. Steel types are immune to poison but that doesnt really help the trainer himself. 
Voltorb could generate electricity for devices.
I dont think any Pokémon survived that can generate food. 
For transportation i look at dragonite and aerodactyl. 

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