Ten Ideas that need development

These are 10 ideas which might make some money:

1. A mobile download idea
2. Making Gray Squirrels infertile
3. Recycling software licences
4. An e-mail address directory (like a telephone directory)
5. Reduce lighting on motorways
6. Making cheaper solar panels
7. Thermo-plugs
8. Overcoming boredom on planes
9. Supplying Ethnic cookery books
10. Can crushing

Since producing this list I have had an additional idea associated with item 4. We have telephone directories for landlines and there are a whole host of Directory enquiry services both on the internet and by phone. Why is there not a directory for mobiles?