I'm not sure what you mean by "geocaching app", but if you mean how can you get more than 1000 caches into GSAK, you can use a combination of:
1) Pocket Queries: you are allowed up to 5 PQ's per day of up to 1000 caches each, for a total of up to 5,000 caches per day. You can use Geocaching.com Access>Download Pocket Queries to retrieve and load these PQ's into GSAK (after you've set them up at Geocaching.com).
To avoid duplication in the Pocket Queries, set up your queries by "date placed". Click here for a link to a good explanation of how to do that, and click here for a GSAK macro that will calculate the dates to use in each PQ.
2) Geocaching.com Access>Get Geocaches: you are allowed up to 6000 caches per day,
for a total of up to 11,000 caches per day! If you set up two sets of different queries and run them every other day, you could get up to 22,000 caches per week. Create three sets of queries and run each every third day and you can get up to 33,000 caches per week.
Once you have the caches in GSAK, you can use filters to select caches in a certain area. For example, if you wanted to view the caches between 15 and 20 miles from your current center point, you would go to Search>Filter and use these settings:
1) Pocket Queries: you are allowed up to 5 PQ's per day of up to 1000 caches each, for a total of up to 5,000 caches per day. You can use Geocaching.com Access>Download Pocket Queries to retrieve and load these PQ's into GSAK (after you've set them up at Geocaching.com).
To avoid duplication in the Pocket Queries, set up your queries by "date placed". Click here for a link to a good explanation of how to do that, and click here for a GSAK macro that will calculate the dates to use in each PQ.
2) Geocaching.com Access>Get Geocaches: you are allowed up to 6000 caches per day,
for a total of up to 11,000 caches per day! If you set up two sets of different queries and run them every other day, you could get up to 22,000 caches per week. Create three sets of queries and run each every third day and you can get up to 33,000 caches per week.

Once you have the caches in GSAK, you can use filters to select caches in a certain area. For example, if you wanted to view the caches between 15 and 20 miles from your current center point, you would go to Search>Filter and use these settings:
