The verdict in three sentences
For a network of agents working outside coverage around Bamako, or any West African field project funded from Europe, an offline-first PWA stores every entry on the phone and syncs automatically once 3G returns. A medium-complexity Kolonell app with deferred sync and conflict handling costs 4,000,000 to 7,000,000 FCFA (6,100 to 10,670 EUR) and ships in 10 to 14 weeks. If your need is limited to questionnaires, KoboToolbox or ODK are enough and far cheaper; custom development is justified once balances, receipts, business rules or integration with your central system come in.
Existing tool or custom app
The first decision is not technical: it depends on what your agents actually do in the field. Collecting answers is a standard need; taking payments or updating a client file is not. For donor-funded projects, this table also helps justify the budget line to the funder.
| Option | Indicative 2026 cost | Offline | Business logic (balances, receipts, approvals) | Best for |
|---|---|---|---|---|
| Paper forms re-keyed | 150,000 FCFA per month per data entry clerk | Yes | No, frequent errors | Under 200 forms a month |
| KoboToolbox | Free for humanitarian use, paid plans otherwise | Yes | Limited | Surveys, M&E |
| Self-hosted ODK Central | Server 25,000 to 75,000 FCFA per month | Yes | Limited | High-volume surveys |
| Simple Kolonell app | 2,500,000 to 4,000,000 FCFA (3,810 to 6,100 EUR) | Yes, one form type | Basic | One process, under 30 agents |
| Medium Kolonell app | 4,000,000 to 7,000,000 FCFA (6,100 to 10,670 EUR) | Yes, conflicts handled | Full | Collection, payments, 30 to 300 agents |
| Complex Kolonell app | 7,000,000 to 15,000,000+ FCFA (10,670 to 22,870+ EUR) | Yes | Full, multi-country, ERP integrations | Regional networks |
What makes an app truly usable offline
Reliable offline mode is more than caching the page. You must decide who wins when two agents edit the same record, what to do with a 4 MB photo on a limited data plan, and how to reassure agents about what has actually been sent.
| Field requirement | Technical answer | 2026 benchmark |
|---|---|---|
| Entry-level Android phones | Lightweight PWA, no app store install | Device at 50,000 to 80,000 FCFA, 2 GB RAM |
| Local storage | Encrypted IndexedDB on the phone | 2,000 to 5,000 offline records with ease |
| Deferred sync | Send queue with resume after drop-out | 100 records without photos: about 200 KB |
| Photos | Compression before storage | 4 MB reduced to 100 to 200 KB |
| Edit conflicts | Timestamps, per-field rules, supervisor arbitration | Under 1% of records in conflict with well-split territories |
| 3G mobile data | Optimised first load, partial updates | First load 1 to 2 MB, then a few KB |
| Proof of sending | Visible status per record, timestamped receipt | Zero records lost on theft or failure once synced |
Kolonell maintenance at 35,000, 75,000 or 120,000 FCFA (50, 110 or 180 EUR) a month then covers updates, sync monitoring and supervisor support. Managed hosting runs 25,000 to 75,000 FCFA a month depending on volume.
Mini case study
Mariam, head of a 60-agent collection network around Bamako (illustrative persona), uses paper forms re-keyed by 2 clerks at 150,000 FCFA a month each, i.e. 300,000 FCFA (460 EUR) a month, with 10 to 15 days before figures reach head office. A medium app with payments, receipts and deferred sync is quoted at 5,500,000 FCFA (8,380 EUR), plus 75,000 FCFA a month for maintenance. The 60 agents already have Android phones. Net saving: 300,000 minus 75,000, i.e. 225,000 FCFA (340 EUR) a month, giving payback of about 24 months on re-keying alone. The main gain lies elsewhere: data at head office within 24 hours instead of two weeks, and cash discrepancies spotted the same day.
FAQ
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Why a PWA rather than a native Android app?
A PWA installs from a simple link, updates without an app store and weighs a few MB. A native app often costs 20 to 40% more for equivalent field use.
How many days can an agent stay offline?
On a 32 GB device, several weeks with no problem. In practice, an alert is set beyond 3 days without sync to limit loss risk.
What if a phone is stolen?
Local data is encrypted and the session can be revoked remotely. Only records not yet synced are lost, hence syncing at every pass through covered areas.
Can we start with KoboToolbox and migrate later?
Yes, it is often a good 2 to 3 month test. Data exported as CSV or via API can be imported into the custom app at switchover.
How long for a full rollout?
Allow 10 to 14 weeks of development, then a 2 to 3 week pilot with 5 to 10 agents before equipping the whole network.
Let's scope your project. Tell us the number of agents, the forms to capture and the areas covered: we price your offline app from 4,000,000 to 7,000,000 FCFA (6,100 to 10,670 EUR) for a medium scope, field pilot included, delivered in 10 to 14 weeks. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
