There are 3 possible parents that could be used in an interspecific cross and still yield edible fruit in the F1: S. Pimpinellifolium, S. Galapagense, and S. Cheesmaniae. S. Pimpinellifolium is widely considered to be the progenitor of the domestic tomato. Crosses with Pimpinellifolium are easily made, fully fertile, and can bring desirable genetics to the table. Unfortunately, Pimpinellifolium is small fruited which is a highly dominant trait. Crosses involving S. Galapagense and S. Cheesmaniae bring an increasing number of undesirable traits which limit potential to make domestic vs wild crosses that have production potential as F1's.
I have two crosses currently segregating in my garden. The most interesting is Piennolo del Vesuvio X LA0417 (S. Pimpinellifolium). I have segregation for foliage disease tolerance that is way beyond anything I've seen in any currently available domestic tomato. Of 16 plants grown out this year, 2 are highly resistant to septoria. One of the two is a slightly nippled oval fruit very similar to Piennolo, the other is a round 1 inch diameter fruit. The other plants in the group include 2 that were totally decimated by foliage disease and the rest that have varying levels of susceptibility. The nippled fruits from the disease tolerant plant are intriguing, they ripen with a glossy shine that I have not seen in a tomato before.
http://www.nature.com/ng/journal/v46...l/ng.3046.html